fix Oracle Log Analytics output plugin 400 Bad Request issue

[handsomecheung]

Fresh the variable tmp_sds (which is still holding info for header host) before handle the new header x-content-sha256.

Fixes #8684

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Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change

[SERVICE]
  flush 1

[INPUT]
  Name   dummy

[Output]
  Name oracle_log_analytics
  Match *
  Namespace ${namespace}
  config_file_location /mnt/oci-config
  oci_la_log_group_id ${group_id}
  oci_la_log_source_name source-name
  tls On
  tls.verify Off

• Debug log output from testing the change

[2024/04/08 14:11:48] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] placed request
[2024/04/08 14:11:48] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] request header POST /20200601/namespaces/nxxxxxxx0/actions/uploadLogEventsFile?logGroupId=ocid1.loganalyticsloggroup.oc1.ap-tokyo-1.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx&payloadType=JSON HTTP/1.1
host: loganalytics.ap-tokyo-1.oci.oraclecloud.com
date: Mon, 08 Apr 2024 14:11:48 GMT
x-content-sha256: loganalytics.ap-tokyo-1.oci.oraclecloud.com
[2024/04/08 14:11:48] [ info] [output:oracle_log_analytics:oracle_log_analytics.0] Unable to parser error response. reponse is not valid json
[2024/04/08 14:11:48] [error] [output:oracle_log_analytics:oracle_log_analytics.0] loganalytics.ap-tokyo-1.oci.oraclecloud.com:443, retry=false, HTTP status=400
<h1>Bad Message 400</h1><pre>reason: Illegal character CNTL=0x0</pre>
[2024/04/08 14:11:48] [debug] [out flush] cb_destroy coro_id=0
[2024/04/08 14:11:48] [debug] [retry] new retry created for task_id=0 attempts=1
[2024/04/08 14:11:48] [ warn] [engine] failed to flush chunk '217570-1712585507.215377216.flb', retry in 7 seconds: task_id=0, input=dummy.0 > output=oracle_log_analytics.0 (out_id=0)
[2024/04/08 14:11:49] [debug] [task] created task=0x7fd7400d1230 id=1 OK
[2024/04/08 14:11:49] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] task_id=1 assigned to thread #0
[2024/04/08 14:11:49] [debug] [input chunk] update output instances with new chunk size diff=36, records=1, input=dummy.0
[2024/04/08 14:11:49] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] payload={"logEvents":[{"logSourceName":"poc-app-file","logRecords":["dummy"]}]}
[2024/04/08 14:11:49] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] lg_id=ocid1.loganalyticsloggroup.oc1.ap-tokyo-1.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
[2024/04/08 14:11:49] [error] [/root/fluent-bit/src/flb_sds.c:43 errno=12] Cannot allocate memory
[2024/04/08 14:11:49] [error] [/root/fluent-bit/plugins/out_oracle_log_analytics/oci_logan.c:609 errno=12] Cannot allocate memory
[2024/04/08 14:11:49] [error] [output:oracle_log_analytics:oracle_log_analytics.0] unable to compose uri for logGroup: ocid1.loganalyticsloggroup.oc1.ap-tokyo-1.xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx logSet: (null)
[2024/04/08 14:11:49] [debug] [output:oracle_log_analytics:oracle_log_analytics.0] full_uri=(null)

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[edsiper]

Thanks for this contribution. Change requests:

• extra variable initialization is not needed
• fix the subject of the commit, it must start with: out_oracle_analytics: ...
• sign off the commits (DCO error)