IB/ucma: Take the network namespace from the process

Add support for network namespaces from user space. This is done by passing
the network namespace of the process instead of init_net.

Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Yotam Kenneth <yotamke@mellanox.com>
Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Guy Shapiro <guysh@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>