fix remove interface logic and update_ip logic

Previously, the code would only update remove an interface if the subnet
was the first one found by the db.  This fix searches all fixed_ips for
a matching subnet.

Additionally, this change also updates the update_port logic to enable a
user to update the IPs associated with router_port.

Change-Id: I4b86c39c574ac12bead918b1a288075bd58610a4
add support for adding same net subnets to rtr int

This change updates the l3_logic to add subnets to exisiting
router ports if they share a network.

Change-Id: Iacd5a4dc02128366f9217a720712af9d83758de8
Merge pull request #4 from markmcclain/dh_g_rc

Dh g rc