volser transaction object race conditions

volser transaction object race conditions

Fix the transaction object races between VolMonitor and the
volume operation procedures which can cause the volume
server to crash.

Add a per transaction object mutex to safely set the
transaction call pointer and name. Fix VolMonitor to safely
traverse the transaction list and to access the call pointer
and last proc name while copying info to send to the vos
client.  Fix the sleep thread to safely access the last proc
name.

FIXES 125479

Change-Id: I59595b93522d111b6a771d3d93c246bfc2ce65de
Reviewed-on: http://gerrit.openafs.org/718
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>