Improves exception message when alarmer is restarted

[kakwok]

The watchthreads throw null pointer exception from this line:
https://github.com/HCALRunControl/levelOneHCALFM/blob/integration/src/rcms/fm/app/level1/HCALEventHandler.java#L2493
Would be better to get more descriptive exception messages other than null pointer exception.

2017-06-30 12:35:18 and 428 ms : cms.hcalpro.rcms.fm.app.level1.HCALEventHandler
ERROR: AlarmerWatchThread(): got an exeption with stacktrace:java.lang.NullPointerException    at rcms.fm.app.level1.HCALEventHandler$AlarmerWatchThread.run(HCALEventHandler.java:2493)
2017-06-30 12:35:18 and 428 ms : cms.hcalpro.rcms.fm.app.level1.HCALEventHandler
ERROR: [HCAL HCAL_LEVEL_1] Error! Got an exception: AlarmerWatchThread()...
Here is the exception: null