[AMBARI-22771] Ambari loads ambari.properties using ISO 8859-1 encoding

[adoroszlai]

What changes were proposed in this pull request?

Specify UTF-8 encoding when reading ambari.properties. Non-Latin1 characters can occur in several properties if customised, eg. in any directory or file name.

How was this patch tested?

• Added unit test, which passes fine:

[INFO] Tests run: 59, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 5.718 s - in org.apache.ambari.server.configuration.ConfigurationTest

• Manually tested according to steps in bug description:

$ ls -la /etc/ambari-server/conf/password.*
-rw-r-----. 1 root root 7 Jan 11 11:04 /etc/ambari-server/conf/password.őőő
$ ambari-server start
...
DB configs consistency check: no errors and warnings were found.
Ambari Server 'start' completed successfully.

• Deployed a simple cluster via blueprint as a smoketest.