LU-13006 jobid: enhance tests to check per-session jobids.

LU-13006 jobid: enhance tests to check per-session jobids.

Lustre allows per-session jobids by writing to "jobid_this_session".

The upstream-linux client does *not* support jobids using the process
environment.

Update the sanity tests to recognize this.

1/ Allow setting jobid_var=USER to fail - if it fails, don't
   test use of envionment variables
2/ Check if "jobid_this_session tests - if it does, check
   that it is used for generating jobids.
3/ Some tests use jobid_var to test general assignment
   to config values.  Change those to use jobid_name if
   it is available.

Also if jobid_var is set to 'session' and jobid_name contains %j -
use jobid_name as is done when jobid_var is a variable name.

Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia7d01b8ffb9c6c910d2ce8f0615c802485604bf9
Reviewed-on: https://review.whamcloud.com/39656
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>