out_stackdriver: fix access token caching

[ridwanmsharif]

This fixes the access token caching in the out_stackdriver plugin.

Signed-off-by: Ridwan Sharif [email protected]

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

• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

==20035== Memcheck, a memory error detector
==20035== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==20035== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==20035== Command: bin/fluent-bit -v --config /run/google-cloud-ops-agent-fluent-bit/fluent_bit_main.conf --parser /run/google-cloud-ops-agent-fluent-bit/fluent_bit_parser.conf --log_file /var/log/google-cloud-ops-agent/subagents/logging-module.log --storage_path /var/lib/google-cloud-ops-agent/fluent-bit/buffers
==20035== 
Fluent Bit v2.0.7
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

==20035== Warning: client switching stacks?  SP change: 0xaff49c8 --> 0x64bf260
==20035==          to suppress, use: --max-stackframe=78862184 or greater
==20035== Warning: client switching stacks?  SP change: 0x64bf1d8 --> 0xaff49c8
==20035==          to suppress, use: --max-stackframe=78862320 or greater
==20035== Warning: client switching stacks?  SP change: 0xaff49c8 --> 0x64bf1d8
==20035==          to suppress, use: --max-stackframe=78862320 or greater
==20035==          further instances of this message will not be shown.
^C[2022/12/20 23:08:27] [engine] caught signal (SIGINT)
==20035== 
==20035== HEAP SUMMARY:
==20035==     in use at exit: 108,091 bytes in 3,682 blocks
==20035==   total heap usage: 26,148 allocs, 22,466 frees, 58,572,379 bytes allocated
==20035== 
==20035== LEAK SUMMARY:
==20035==    definitely lost: 0 bytes in 0 blocks
==20035==    indirectly lost: 0 bytes in 0 blocks
==20035==      possibly lost: 0 bytes in 0 blocks
==20035==    still reachable: 108,091 bytes in 3,682 blocks
==20035==         suppressed: 0 bytes in 0 blocks
==20035== Rerun with --leak-check=full to see details of leaked memory
==20035== 
==20035== For counts of detected and suppressed errors, rerun with: -v
==20035== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

[github-actions]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[igorpeshansky]

LGTM

[braydonk]

There is a chance this could fix #7552 (or at least one of the segfaults listed). LGTM so I am going to merge.