iocShutdown() should only stop threads and cleanup
if the IOC was started with iocBuildIsolated().
If iocBuild() is used then only close CA links
as was done previously.
This is needed as some device support calls epicsExit()
(while holding a record lock). This make it impossible
to run the full iocShutdown without deadlocking
in scan/callback shutdown, or segfaulting
in doFreeRecord() or dbLockCleanupRecords()
Michael Davidsaver
d35780888a