LU-2524 test: Test suite clean up for replay-single

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
Modified directory and file names to use $tdir and $tfile
Add check for and call `error` and/or add error messages for a
variety of common functions.
Replace `…` with $(...)
Removed linefeed escape after |, ||, & and && operators.
Remove test dependencies between tests 4a and 4b

Test-Parameters: testlist=replay-single alwaysuploadlogs envdefinitions=SLOW=yes mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Ib09102e50f855550db801180be3f7fc42911191a
Reviewed-on: http://review.whamcloud.com/13170
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>