LU-9201 test: avoid long sleeps in mount_facet()

LU-9201 test: avoid long sleeps in mount_facet()

Reduce the long sleep during mount since this was fixed via
patch https://review.whamcloud.com/24845 for LU-7481.

This reduces one llmount.sh time from 62s to 37s (2 MDTs, 4 OSTs),
and removes about 800s from each conf-sanity run (201x 4s sleeps
due to "Commit the device label" in a recent test log).

Test-Parameters: trivial testlist=conf-sanity,conf-sanity,conf-sanity
Test-Parameters: trivial testlist=conf-sanity,conf-sanity,conf-sanity
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ib51858a00b935c4f7e473cead117e7d59c3ebbe5
Reviewed-on: https://review.whamcloud.com/26021
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>