Add a gate-specific tox env for functional tests

The functional gate jobs (*-neutron-dsvm-functional) need special
configuration (e.g. OS_SUDO_TESTING, OS_ROOTWRAP_CMD) to run tests.
This patch adds a new gate-specific tox env (tox -e dsvm-functional)
that sets the appropriate values and allows easy duplication of the
results of the upstream job on a host that has successfully run
devstack with neutron enabled.

A new configuration option, OS_FAIL_ON_MISSING_DEPS, is also set by
the dsvm-functional tox env to ensure that dependency failures will
result in failures rather than skips when run in the gate.

Change-Id: Idbfef1ba72ed129a3021509c7969e2685b8a6d09
Partial-bug: #1336172
Mock out tunnel_sync in test to avoid sleeping

The tunnel_sync call in the daemon loop for the ovs tunnel
tests blocks for 30 seconds. This patch mocks it out to stop
that.

Closes-Bug: #1340570
Change-Id: I58c3907ed564413a8251bc1bb7922e25f673db18
Validate expected parameters in add/remove router interfaces

The add and remove router interface methods check that interface_info
is not empty but don't check if it contains any of expected parameters:
port_id and subnet_id
This patch adds a helper method to validate that interface_info contains
at least one of the expected parameters
Include a unit test for the empty port_id and subnet_id case

Closes-Bug: #1325982

Change-Id: Ia370565235a33a847704b972c875d8f1573306c0
Dnsmasq config files syntax issue when dhcp_domain is empty

When using dhcp-agent with the following property dhcp_domain=""
addn_hosts and host files genererated for Dnsmasq have wrong syntax
concerning hostname parameter (dot char at the end).

As described in RFC-952 the hostname grammar is as follows:
<hname> ::= <name>*["."<name>]
<name>  ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]
Hence it can't be conclude with a dot char.

Dnsmasq process is waiting for a hostname (2nd parameter) in the
following files:
"addn_hosts" file contains:
   20.0.0.3 host-20-0-0-3. host-20-0-0-3
"host" file contains:
   fa:16:3e:bf:e1:e4,host-20-0-0-3.,20.0.0.3

With the patch you will get:
"addn_hosts":
   20.0.0.3 host-20-0-0-3 host-20-0-0-3
"host":
   fa:16:3e:bf:e1:e4,host-20-0-0-3,20.0.0.3

Change-Id: I4c10169019becaed6b2968b74f03ef356244a057
Closes-Bug: #1326256
Merge "Dnsmasq config files syntax issue when dhcp_domain is empty"
Merge "Add a gate-specific tox env for functional tests"
Merge "Validate expected parameters in add/remove router interfaces"
Merge "Mock out tunnel_sync in test to avoid sleeping"