LU-8182 mdt: check connection data properly

LU-8182 mdt: check connection data properly

For mdt_obd_connect() case, the parameter @data should never be
NULL, so drop the redundant check of "data != NULL", replace it
with "LASSERT(data != NULL);"

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ia6754752527e69c89e7a40d3d012232eaba94d3e
Reviewed-on: http://review.whamcloud.com/20391
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>