test/nvmf: let modprobe pass if no module found

In fedora 27 4.17.11 kernel, there is no ib_ucm module.
So let modprobe pass if no ib_ucm.

Change-Id: I793802f65263f0f8e3ef0097250fd9ca3cc9ffdc
Signed-off-by: Liang Yan <liang.z.yan@intel.com>
Reviewed-on: https://review.gerrithub.io/423625


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Chandler-Test-Pool: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>