Allow the dounmount() to proceed even for doomed coveredvp.

In dounmount(), before or while vn_lock(coveredvp) is called, coveredvp
vnode may be VI_DOOMED due to one of the following:
- other thread finished unmount and vput()ed it, and vnode was chosen
  for recycling, while vn_lock() slept;
- forced unmount of the coveredvp->v_mount fs.
In the first case, next check for changed v_mountedhere or mnt_gen counter
would be successfull. In the second case, the unmount shall be allowed.

Submitted by:	sobomax
MFC after:	2 weeks

0 files changed, 0 insertions, 0 deletions