Need to check if on_send_comp callback is assigned
Signed-off-by: Or Kehati <ork@mellanox.com>

Change-Id: I8427860f1d191c5e56eac4c7e30af6638f3900cd
code optimization

Change-Id: Id2b551f98c0391f996d4b14e25d367dc66be1612
Signed-off-by: Eyal Salomon <esalomon@mellanox.com>