RFR: 8145294: TestLogRotation.java triggers a race in the UL framework

[Marcus Larsson]

Hi,

Please review the following patch to fix a race in file rotations with UL.
Summary:
freopen and fwrite are not safe to use concurrently and hence the VM 
might crash if a thread tries to write during a rotation. Writing and 
rotating needs to be properly synchronized, but using a Mutex is 
problematic here because the synchronization must be usable already at 
argument parse time. The patch replaces the previously used mutexes with 
semaphores (like with the LogConfiguration_lock case). LogFileOutputs 
are now rotatable at any time and the LogOutput interface has been 
simplified to reflect this.

Webrev:
http://cr.openjdk.java.net/~mlarsson/8145294/

Issue:
https://bugs.openjdk.java.net/browse/JDK-8145294

Testing:
TestLogRotation in RBT and locally

Thanks,
Marcus