util: Rename virObjectLockRead to virObjectRWLockRead

util: Rename virObjectLockRead to virObjectRWLockRead

Since the class it represents is based on virObjectRWLockableClass
and in order to make sure we differentiate just in case anyone somehow
believes they could use virObjectLockRead for a virObjectLockableClass,
let's rename the API to use the RW in the name. Besides the RW locks
refer to pthread_rwlock_{init|rdlock|wrlock|unlock|destroy} while the
other locks refer to pthread_mutex_{init|lock|unlock|destroy}.

Signed-off-by: John Ferlan <jferlan@redhat.com>