LU-7372 tests: re-enable replay-dual test_26

LU-7372 tests: re-enable replay-dual test_26

Re-enable test_26 since it was just the unfortunate victim of
either test_24 or test_25 causing MDS unmount to hang.

Lustre-change: https://review.whamcloud.com/43982
Lustre-commit: TBD (from 0f509199a25db416759c3bbcce85c6b79d623585)

Test-Parameters: trivial testgroup=review-dne-part-2
Test-Parameters: testgroup=review-dne-part-2
Test-Parameters: testgroup=review-dne-part-2
Test-Parameters: testgroup=review-dne-part-2
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ib944028e798488c425501f0c48bf812fc13ebbe5
Reviewed-on: https://review.whamcloud.com/43978
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>