Update buildbot_tool and builders.pyl templates to remove 'master_type'.

Update buildbot_tool and builders.pyl templates to remove 'master_type'.

With the impending changes to builders.pyl-based buildbot masters to
support multiple schedulers, we will no longer need to support different
templates for tryservers and waterfall masters, since a given master
may have both kinds of bots (and the distinction isn't really meaningful
in the code, though it can still be useful to users).

This change removes the 'master_type' field from the builders.pyl
format, and now all of the master classes will explicitly note
whether buildbucket_bucket and service_account_file were set (or not).

R=nodir@chromium.org
BUG=492876
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295462

[Dirk Pranke, 2015-05-29 01:55:38]

This CL does some trivial cleanup prior to the main work to add support for
multiple schedulers.

https://codereview.chromium.org/1153203003/diff/1/scripts/master/unittests/ma...
File scripts/master/unittests/master_gen_test.py (left):

https://codereview.chromium.org/1153203003/diff/1/scripts/master/unittests/ma...
scripts/master/unittests/master_gen_test.py:87: def test_tryserver(self):
We'll add an equivalent test back in the follow up patch, but in this CL it
wasn't testing anything interesting.

[Dirk Pranke, 2015-05-29 01:55:58]

Oh, and the corresponding doc change is in
https://codereview.chromium.org/1143393004/ .

[nodir, 2015-05-29 03:31:54]

lgtm

[Dirk Pranke, 2015-05-29 20:40:30]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2015-05-29 20:40:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1153203003/1

[commit-bot: I haz the power, 2015-05-29 20:45:35]

Committed patchset #1 (id:1) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=295462