Fix enum undef ts bug35

[bhill-slac]

When support for propEventCB was added to the gateway, it subscribed to DBR_CTRL_* but calls both runDataCB and runValueDataCB. Since the DBR_CTRL_* events have zero in the timestamp fields and the value_data_callbacks assign the gdd from the DBR_CTRL* event to the gatePv value gdd, it can step on the timestamp from the DBR_TIME_* event.

I suspect the code in gatePvData::propEventCB was ignoring the first propEvent to avoid this bug but some cases get through and set the timestamp fields to zero, in particular mbbi and mbbo records.

This fix creates to subcriptions for DBE_PROPERTY events, one DBR_CTRL* subscription w/ propDataCB, and a DBR_TIME* subscription w/ propEventCB.

[ralphlange]

This pull request fails the tests on all different architectures.
Main issue, which seems directly related to the changes in this PR:

make[3]: Entering directory '/home/runner/work/ca-gateway/ca-gateway/testTop/pyTestsApp/O.linux-x86_64'
  ======================================================================
  FAIL: Monitor PV (imitating CS-Studio) through GW - change value and properties directly - check CTRL structure consistency
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/home/runner/work/ca-gateway/ca-gateway/testTop/pyTestsApp/TestCSStudio.py", line 93, in testCSStudio_ValueAndPropMonitor
      self.assertTrue(are_diff == False,
  AssertionError: False is not true : At update 3 (change value), received structure updates differ:
  	Element 'value' : GW has '0.0', IOC has '10.0'
  	Element 'ftype' : GW has '34', IOC has '20'
  	Element 'status' : GW has '17', IOC has '4'
  	Element 'severity' : GW has '3', IOC has '1'
  	Element 'timestamp' : GW has '631152000.0', IOC has '1653[43](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:44)5554.5943'
  	Element 'posixseconds' : GW has '6311[52](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:53)000.0', IOC has '16[53](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:54)4355[54](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:55).0'
  	Element 'nanoseconds' : GW has '0', IOC has '[59](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:60)4300114'
  
  ======================================================================
  FAIL: DBE_PROPERTY monitor on an ai - value changes generate no events; property changes generate events.
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/home/runner/work/ca-gateway/ca-gateway/testTop/pyTestsApp/TestDBEProp.py", line [60](https://github.com/epics-extensions/ca-gateway/runs/6583342460?check_suite_focus=true#step:8:61), in testPropAlarmLevels
      self.assertTrue(self.eventsReceivedGW == 1, 'GW events expected: 1; received: ' + str(self.eventsReceivedGW))
  AssertionError: False is not true : GW events expected: 1; received: 2
  
  ----------------------------------------------------------------------

Please either fix the changes or the test.

[bhill-slac]

Looks like the test just needed to adjust the expected eventsReceived counts.
This is expected as the gateway w/ this branch is doing two subscriptions instead of one.

[ralphlange]

Thanks a lot, Bruce!
I had an idea but was not 100% sure if the code or the test needed changing.