Remove redundant default=None for config options

By default the cfg modules set the default value as None. There
is no reason to set this.

Change-Id: I58e09e01760b573612c2ee169a8dd1784fd36a82
Support 'infinite' dhcp_lease_duration

Process a dhcp_lease_duration value of -1 as 'infinite'
when setting the dnsmasq dhcp-range values to support
cases where it is undesirable for instance dhcp leases
to expire.

DocImpact

Closes-Bug: #1315430
Change-Id: I1cc3cfebfec355014e6d5b5cbd656a1300c43c0b
Disallow regular user to update firewall's shared attribute

Shared firewalls should only be operable by  admins.
Currently only admin can provide shared attribute at firewall creation,
so update_firewall should be consistent with that as well.

Change-Id: I093743514637824207b375d724404d51f778d012
Closes-Bug: #1323322
Revert "fix openvswitch requirement check"

This reverts commit be340d1bab015c47650687f97393c6c9015fb537.

The fix did not fix anything.
See comments at
https://review.openstack.org/#/c/95592/

Change-Id: I2926acf4b0a7020a7ad3237e6d03d5b78bfcb6c4
Merge "Remove redundant default=None for config options"
Merge "Support 'infinite' dhcp_lease_duration"
Merge "Revert "fix openvswitch requirement check""