gfs2: Initialize gl_no_formal_ino earlier

Set gl_no_formal_ino of the iopen glock to the generation of the
associated inode (ip->i_no_formal_ino) as soon as that value is known.
This saves us from setting it later, possibly repeatedly, when queuing
GLF_VERIFY_DELETE work.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>