LU-12489 tests: Recategorize some "Slow" tests as normal.

LU-12489 tests: Recategorize some "Slow" tests as normal.

replay-single 44b is really fast now
replay-ost-single 8[ab] both take under a minute in my testing
ost-pools 23b only takes a minute now and test 18 is still
          under 10 minutes to bother excluding it.

Change-Id: I57a35c39cadd1728c38d332d83cbe50da6d6a8fe
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/35367
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>