tests: Add tests of mfscgiserv

This commit adds two tests of mfscgiserv.

First test is in ShortSystemTests suite and checks if there
are no traceback entries in html files generated by mfscgiserv. It also
validates generated html pages with tidy.

Second test is in SanityChecks suite and validates mfs.cgi
using pylint.

Change-Id: Id35291dcf018526d37ef0dd0f0113a9f06689f3a