=act #15488 Removed guard around _logLevel

This patch removes a lock around the getter of _logLevel. The setter is
still guarded for consistency. Note that out of thin-air reads, while
not excluded under the current JMM, are forbidden by current hardware.

Signed-off-by: Duarte Nunes <duarte.m.nunes@gmail.com>
Merge pull request #15546 from ktoso/port-removeGuardOnLoglevelRead-ktoso

=act #15488 Removed guard around _logLevel (for validation)