ubik: Drop dbase versionLock during I/O and sleeps

ubik: Drop dbase versionLock during I/O and sleeps

Currently we hold versionLock during all ubik network I/O and while we
are sleeping for whatever reason. For pthreaded ubik, to allow other
things to happen during those times, drop the lock and reacquire when
we hit the net or sleep.

Change-Id: I414b3adfadc0bb506b98e8677ec5dfbb269e0129
Reviewed-on: http://gerrit.openafs.org/2107
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>