LU-12131 tests: properly handle GSS in server failover

LU-12131 tests: properly handle GSS in server failover

In case of server failover, a number of aspects must be handled when
GSS based features (SSK or Kerberos) are activated:
- lsvcgssd daemon must be restarted;
- targets must be mounted with proper skpath option;
- permissions on keys must be adjusted.
When service is initially started, all that is managed in setupall().
fail() and facet_failover() have to be improved to take GSS aspects
into account.

Lustre-change: https://review.whamcloud.com/35041
Lustre-commit: 1cbfb44fb59945da62acbb672330fde5c75ddc98

Test-Parameters: envdefinitions=SHARED_KEY=true testlist=sanity,recovery-small,sanity-sec
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I8db686f406629c7eec655496cf83c0539c1bfb33
Reviewed-on: https://review.whamcloud.com/35534
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>