GFS2: Do not reset flags on active reservations

When we used try locks for rgrps on block allocations, it was important
to clear the flags field so that we used a blocking hold on the glock.
Now that we're not doing try locks, clearing flags is unnecessary, and
a waste of time. In fact, it's probably doing the wrong thing because
it clears the GL_SKIP bit that was set for the lvb tracking purposes.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>