LU-2524 test: Code clean up for conf-sanity

The patch modifying the tdir variable to a single directory
has landed; http://review.whamcloud.com/#/c/8123/. We can
now conduct miscellaneous cleanup including:

Remove the `-p` (parents) option from many calls to mkdir
Replace `lfs setstripe` with $SETSTRIPE
Replace `lfs getstripe` with $GETSTRIPE
Replace `lctl` with $LCTL
Added check for and call `error` and/or added error messages
for a variety of common functions.
Replace `…` with $(...)
Remove linefeed escape after |, ||, & and && operators.
Modify directory and file names to use $tdir and $tfile
Remove 'mkdir -p $MOUNT' when 'mount_client $MOUNT' is
called right before or after mkdir

Test-Parameters: alwaysuploadlogs \
envdefinitions=SLOW=yes testlist=conf-sanity

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: I94bd51ce2d2f225736e12c4f9ac1a86a3d8a23d8
Reviewed-on: http://review.whamcloud.com/10530
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>