pvscan: retry VG refresh before autoactivation if it fails

pvscan: retry VG refresh before autoactivation if it fails

There's a tiny race when suspending the device which is part
of the refresh because when suspend ioctl is performed, the
dm kernel driver executes (do_suspend and dm_suspend kernel fn):

  step 1: a check whether the dev is already suspended and
          if yes it returns success immediately as there's
          nothing to do
  step 2: it grabs the suspend lock
  step 3: another check whether the dev is already suspended
          and if found suspended, it exits with -EINVAL now

The race can occur in between step 1 and step 2. To prevent
premature autoactivation failure, we're using a simple retry
logic here before we fail completely. For a complete solution,
we need to fix the locking so there's no possibility for suspend
calls to interleave each other to cause this kind of race.

This is just a workaround. Remove it and replace it with proper
locking once we have that in!