LU-11717 tests: exit_status () defect

LU-11717 tests: exit_status () defect

exist_status() should search a word FAIL, otherwise
all the tests skipped due to reason which contains
FAILOVER_MODE have status = 1 and exited with the error.

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-6711
Reviewed-by: Sergey Cheremencev <c17829@cray.com>
Reviewed-by: Alexander Boyko <c17825@cray.com>
Change-Id: I5a69e0a4aed6cc8d75d97fe83c6f304b666701ea
Reviewed-on: https://review.whamcloud.com/33751
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>