IMPALA-7099: xfail test on affected filesystems
IMPALA-7099: xfail test on affected filesystems

As a stopgap, let's xfail the test on filesystems where this
is known to be broken.

Testing:
Tested that the test succeeded and xfailed without and with an fs
prefix, i.e.:

  impala-py.test tests/metadata/test_partition_metadata.py -k unsupport
  FILESYSTEM_PREFIX="s3a://" impala-py.test tests/metadata/test_partition_metadata.py -k unsupport

Change-Id: Ie5dd744d48f099b3b12607ad91454e71733f1c6a
Reviewed-on: http://gerrit.cloudera.org:8080/10566
Reviewed-by: Dan Hecht <20ebd99959f0f6e5dcb0fc319b4d8ef53a16b5fb@cloudera.com>
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>

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