Add a test for #22686

[fungusakafungus]

Tests whether profession-specific items in holsters can be put back once
removed.

Fixes #22686.

• do tests have RL_Classes mod enabled? -> No
• should they? -> yes, added a matrix job to travis to test with RL_Classes mod. More mods can be added later

[fungusakafungus]

So, the new test passes for default dda mod, but it fails for RL_Classes if run locally:

~/src/Cataclysm-DDA](test_holster)$ ./tests/cata_test starting_items --mods=RL_Classes
Starting the actual test at Mon Apr  2 13:41:09 2018

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cata_test is a Catch v1.9.6 host application.
Run with -? for options

-------------------------------------------------------------------------------
starting_items
-------------------------------------------------------------------------------
new_character_test.cpp:93
...............................................................................

new_character_test.cpp:173: FAILED:
  REQUIRE( failures.empty() )
with expansion:
  false
with message:
  wizard ANTIFRUIT  sheath: Couldn't put item back to holster

(it is also the only test that fails with RL_Classes)

What do I do now? Can someone help me to enable tests for other mods? Which mods?
@kevingranade is this test what you meant in #22686 (comment) by "profession consistency
checking"?

[kevingranade]

Yes that's exactly it.

should they?

If you want to fix it go ahead, but it's mergeable without it.

[fungusakafungus]

This one shows the problem in #22686

[fungusakafungus]

Please take another look, I think this is mergable now.
This adds another (10th) matrix job to travis, for running test with selected mods enabled.