tubik: Correct use of flags_cond and version_cond

tubik: Correct use of flags_cond and version_cond

Waiters of flags_cond and version_cond were not doing so correctly;
the correct way is to acquire a lock prior to their respective checks,
and atomically drop/acquire that lock with pthread_cond_wait.
Otherwise, we could miss a wakeup if a flag changed between our check
and when we wait.

To make this possible, make versionLock a normal pthread mutex in
AFS_PTHREAD_ENV, so it is a lock we can pass to pthread_cond_wait.
Make the waiters pass versionLock to pthread_cond_wait, and eliminate
flags_mutex and version_mutex.

Change-Id: Id33a72182b907d069e342cb049e23868ab2f7eb9
Reviewed-on: http://gerrit.openafs.org/1681
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>