update subnet gateway cause wrong DHCP pool calculation

[Martin Pavlásek]

Description of problem:
Later updated subnet gateway leads to IP address conflict with DHCP pool range.

How reproducible:
100%

Steps to Reproduce:
Log in as demo user.
1. Project - Network - Networks - Create Network
2. network "test_net", subnet "test_subnet", network address 10.0.0.0/24, IPv4, tick Disable Gateway, Create
3. click to test_net row, click to Edit Subnet for test_subnet row
4. untick Disable Gateway, gateway IP 10.0.0.1, Next, leave Allocation Pools unchanged, Save

Actual results:
Computed Allocation pools is "10.0.0.1,10.0.0.254", click to Save cause red alert:
Error: Failed to update subnet "10.0.0.0/24": Gateway ip 10.0.0.1 conflicts with allocation pool 10.0.0.1-10.0.0.254

Expected results:
it should exclude the IP of gateway from the DHCP pool, so:
10.0.0.2,10.0.0.254

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/297174

[OpenStack Infra (hudson-openstack)]

Change abandoned by Armando Migliaccio (<email address hidden>) on branch: master
Review: https://review.openstack.org/297174
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.

[Armando Migliaccio (armando-migliaccio)]

This works as intended. If you want to change the pool and clash with the gateway IP, you must update the gateway IP first.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Armando Migliaccio (<email address hidden>) on branch: master
Review: https://review.openstack.org/297174