Add ipaddress in manila requirements
The ipaddress module required by recent ipv6 work:
@@ -9,6 +9,7 @@ alembic>=0.8.10 # MIT
Babel!=2.4.0,>=2.3.4 # BSD
eventlet!=0.18.3,!=0.20.1,<0.21.0,>=0.18.2 # MIT
greenlet>=0.3.2 # MIT
+ipaddress>=1.0.7;python_version<'3.3' # PSF
lxml!=3.7.0,>=2.3 # BSD
netaddr!=0.7.16,>=0.7.13 # BSD
oslo.config!=4.3.0,!=4.4.0,>=4.0.0 # Apache-2.0
