fix user space kernel connection establishment

Redmine issue #393054 : xio connection establishment kernel vs. user
space is broken.

The increased size of io vectors caused memory allocation to fail.
Moved message allocation from kzalloc to vzalloc, also decrease the
amount of FRWR descriptors based on the number of maximal infight
requests.
Also fix the hello_world_mt.

Signed-off-by: Shlomo Pongratz <shlomop@mellanox.com>