[Hot Fix] Ignore org.apache.spark.ui.UISuite tests

#446 faced a connection refused exception from these tests, causing them to timeout and fail after a long time. For now, let's disable these tests.

(We recently disabled the corresponding test in streaming in 7863ecca. These tests are very similar).

Author: Andrew Or <andrewor14@gmail.com>

Closes #466 from andrewor14/ignore-ui-tests and squashes the following commits:

6f5a362 [Andrew Or] Ignore org.apache.spark.ui.UISuite tests