memcached fails to enable ufw when there is no IPv6 support

In an effort to improve quality, we are testing all charms in an automated process.

According to the latest test results by charm http://reports.vapour.ws/charm-tests-by-charm this charm is failing automated testing.

The output can be found here:

http://reports.vapour.ws/charm-tests/charm-bundle-test-10651-results

The 10_deploy_test.py failed with the following output:

* memcached is running
The memcached service is running.
An error occurred communicating with memcached over telnet ec2-54-173-144-188.compute-1.amazonaws.com:11212 [Errno 110] Connection timed out
Traceback (most recent call last):
  File "/var/lib/jenkins/workspace/charm-bundle-test/tmpW8rmfw/memcached/tests/10_deploy_test.py", line 77, in <module>
    tn = telnetlib.Telnet(memcached_address, memcached_port)
  File "/usr/lib/python3.4/telnetlib.py", line 221, in __init__
    self.open(host, port, timeout)
  File "/usr/lib/python3.4/telnetlib.py", line 237, in open
    self.sock = socket.create_connection((host, port), timeout)
  File "/usr/lib/python3.4/socket.py", line 509, in create_connection
    raise err
  File "/usr/lib/python3.4/socket.py", line 500, in create_connection
    sock.connect(sa)
TimeoutError: [Errno 110] Connection timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/jenkins/workspace/charm-bundle-test/tmpW8rmfw/memcached/tests/10_deploy_test.py", line 110, in <module>
    amulet.raise_status(amulet.FAIL, msg=message)
  File "/usr/lib/python3/dist-packages/amulet/helpers.py", line 140, in raise_status
    sys.exit(code)
SystemExit: 1

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/var/lib/jenkins/workspace/charm-bundle-test/tmpW8rmfw/memcached/tests/10_deploy_test.py", line 112, in <module>
    tn.close()
NameError: name 'tn' is not defined

Please investigate this failure and fix the test or the code so it passes automated testing.