Fix failing tests

Factory boy doesn't reset the sequence between tests.
We use a sequence to generate unique IP addresses in the InterfaceFactory.
When the sequence number gets too high, the IP is not in the network
range anymore.

To fix the issue, we reset the sequence number when initializing a new
session.

tests/functional/conftest.py

@@ -82,6 +82,7 @@ def session(db, request):
 
     Rollback any transaction to always leave the database clean
     """
+    factories.InterfaceFactory.reset_sequence()
     connection = db.engine.connect()
     transaction = connection.begin()
     session = common.Session

tests/functional/factories.py

@@ -139,7 +139,10 @@ class NetworkFactory(factory.alchemy.SQLAlchemyModelFactory):
     def last_ip(self):
         net = ipaddress.ip_network(self.address)
         hosts = list(net.hosts())
-        return str(hosts[-5])
+        try:
+            return str(hosts[-5])
+        except IndexError:
+            return str(hosts[-1])
 
 
 class InterfaceFactory(factory.alchemy.SQLAlchemyModelFactory):