Fix gate issues on master

We recently removed nenutron.common.rpc [1] as the rpc module lives in
neutron-lib now. This project was missed because I didn't find
neutron.common.rpc as an import. This patch switches rpc uses over to
neutron-lib.

This also addresses an issue where toxenv fails when it encounters a
non-empty __pycache__ directory. This adjusts the options passed to
find so that it is tolerant of this scenario and allows tox runs to
proceed.

"rm -rf .tox/lower-constraints/*" in testenv command in tox.ini
is unnecessary, so it is dropped too.

[1] https://review.openstack.org/#/c/634790/

Change-Id: I95490cba503d3f3a61bdc28ef63edc82a3ae1be3

neutron_fwaas/tests/unit/services/logapi/agents/l3/test_fwg_log.py

@@ -34,7 +34,7 @@ class FWaaSL3LoggingExtensionInitializeTestCase(base.L3LoggingExtBaseTestCase):
     @mock.patch.object(registry, 'register')
     @mock.patch.object(resources_rpc, 'ResourcesPushRpcCallback')
     def test_initialize_subscribed_to_rpc(self, rpc_mock, subscribe_mock):
-        call_to_patch = 'neutron.common.rpc.Connection'
+        call_to_patch = 'neutron_lib.rpc.Connection'
         with mock.patch(call_to_patch,
                         return_value=self.connection) as create_connection:
             self.fw_l3_log_ext.initialize(

tox.ini

@@ -13,11 +13,9 @@ deps = -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/re
 whitelist_externals =
   sh
   find
-  rm
 commands =
   find . -type f -name "*.py[c|o]" -delete
-  find . -type d -name "__pycache__" -delete
-  rm -rf .tox/lower-constraints/*
+  find . -path "*/__pycache__*" -delete
   {toxinidir}/tools/ostestr_compat_shim.sh {posargs}
 # there is also secret magic in ostestr which lets you run in a fail only
 # mode. To do this define the TRACE_FAILONLY environmental variable.