LU-16516 tests: ONLY and ONLY_REPEAT improvements

LU-16516 tests: ONLY and ONLY_REPEAT improvements

ONLY_REPEAT=N did not work if multiple subtests were selected via
a "base" test number (e.g. "ONLY=118") and that resulted in more
than one subtest being run (e.g. ONLY_118a=true, ONLY_118b=true, ...)
Since the run_one() caller of run_one_logged() is already checking
whether the test should be run or not, don't repeat that check
for ONLY_REPEAT.

Allow ONLY_REPEAT to be used when multiple subtests are specified
via ONLY, even if the subtests are not explicitly listed.

Allow tests in ONLY, EXCEPT, ALWAYS_EXCEPT, and SLOW to be separated
by '+', or ',' in addition to space-separated test numbers.  That
avoids issues with handling space-separated test lists in the shell
or when specified via Test-Parameters (need to use '+' in that case).

Test-Parameters: trivial testlist=sanity env=ONLY=118,ONLY_REPEAT=5
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ieac578c098ae76994a211c7db094dd99923bcc8c
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/50395
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Alex Deiter <alex.deiter@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>