In osm_ucast_mgr, where osm_req_set is called for SwitchInfo,

In osm_ucast_mgr, where osm_req_set is called for SwitchInfo,
fix bug where it copies more memory than it should into the SMP.

While running opensm with valgrind, it was found out that there is a
problem  with osm_req_set function. It clears the madw.data by size of
IB_SMP_DATA_SIZE, but the function doesn't require a payload of this
size. In osm_ucast_mgr there was a call to the function with a payload
of smaller size (for SwitchInfo).

To fix it, payload_size to the osm_req_set was added.

git-svn-id: svn://openib.tc.cornell.edu/gen1@144 ad392aa1-c5ef-ae45-8dd8-e69d62a5ef86