LU-15455 tests: fix [: ==: unary operator expected

LU-15455 tests: fix [: ==: unary operator expected

PARALLEL is not initiallized in recovery-small.
Patch fixes the bash syntax error.

Fixes: 26e8f1137b ("LU-13116 mgc: do not lose sptlrpc config lock")
Fixes: 688d5da6a8 ("LU-12846 mdd: return error while delete failed")
Test-Parameters: trivial env=ONLY="141 143" testlist=recovery-small
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-10679
Change-Id: I495bfd077edf3d15f1d47ccb4723e1de46de94e7
Reviewed-on: https://review.whamcloud.com/46150
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>