BUG #14214: Miscellaneous fixes for tracing.

Cleaned up logic in tracing. We were ending up with out of order trace captures
resulting in broken trace files that didn't work as expected using all ParaView
executables. This was happening because a lot of new code added to smtrace
directly appended to the trace_output stream without flushing the information
currently gathered. Fixed that by streamlining the logic.

Also fixed a leak with trace observer. The observer was in place even after
tracing was stopped. Fixed that.

Change-Id: I805ffd7570c0b79ace9b540504a55c8f5e842b23
pqSMAdaptor not respecting unchecked flag.

pqSMAdaptor was not using unchecked set API for enumeration properties. Fixed
that.

Change-Id: I019f92da909b3bcdaef923f0ed40d930ee97eb74
Merge topic '0014214_fix_python_trace_issues' into next

85dd5a3 pqSMAdaptor not respecting unchecked flag.
e48bf68 BUG #14214: Miscellaneous fixes for tracing.