LU-1471 tests: check rpcidmapd service in setup-nfs.sh

LU-1471 tests: check rpcidmapd service in setup-nfs.sh

The rpcidmapd system service is not in SLES11 distro, which
caused "service: no such service rpcidmapd" error while running
setup-nfs.sh. This patch fixes the above issue by checking the
service before restarting or stopping it.

Test-Parameters: testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I0571d9ce3850fda246c1cd43b6c9019de30398e1
Reviewed-on: http://review.whamcloud.com/3400
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>