LU-9364 test: wait rmultiop_start to start

LU-9364 test: wait rmultiop_start to start

In rmultiop_start, the remote command could be delayed a while,
and wait some time for the command to run.

Test-Parameters: trivial testlist=replay-vbr

Lustre-change: https://review.whamcloud.com/26729
Lustre-commit: f1e337e077b3bc653c91fda0e19a5346ca154705

Change-Id: Ic8beec725edc89a527c74e2033e59e1da0d444c9
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Saurabh Tandan <saurabh.tandan@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/28440
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>