Fixing two comments regarding bind_port in ml2

Fixes two comment lines regarding when bind_port
is called. The correct comment should indicate that
bind_port is called prior to "create_port_precommit or
update_port_precommit" rather than
"create_network_precommit or update_network_precommit".

Change-Id: I5c0cb49efb43b15fdc5a7f88569e19fcf8d72819
Merge "Fixing two comments regarding bind_port in ml2"