winverbs: fix memory violation in SRQ code

Problem reported by Shiqing Fan:

"I got a memory violation error in wv_srq.cpp Query() function around
line 202. It seems using uninitialized verbsData.output_size for
memcpy. The verbsData.input_size is initialized in WvPreQueryQp
(wvuverbs.cpp), and it has a similar memcpy in this function too."

wv_uverbs.cpp should initialize the output_size to 0 in all
WvPre* calls.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>