The MAM integration test setup attepts to set MAM preferences (XEP-0441).
When a server does not support this XEP, the setup phase errors out, preventing
the tests from being executed.
There is no functional reason why tests shouldn't be run when XEP-0441 is not
supported: the tests can run against the default configuration of the MAM
service.
This commit ignores feature-not-implemented errors when MAM
preferences are set.
[Ignore only feature-not-implemented errors, log ignored errors)
Modified-by: Florian Schmaus <flo@geekplace.eu>