Fix gerrit errors from production

This corrects the following errors.

Test fixture errors:

* Unlike the SSH API, the Gerrit REST API does not include
  COMMIT_MSG in the list of files.
* We weren't checking all elements of the (change id, branch,
  project) tuple when searching for change ids
* I observed a race around poll synchronization; I can't figure it out
  so I've added more debug log lines.

Production errors:

* Break after the first successful submit rather than attemping the
  call multiple times in all cases.  This was non-fatal.
* Only attempt to get the remote version if using HTTP.  This was
  non-fatal.
* URLquote search queries (they may contain '#').  The additional CRD
  tests cover this now.
* Coerce the list of files to a list rather than a dict_keys instance.
  The new single file test covers this.

Change-Id: I89a68b2d189b82f0bc64e78fbc875d5628cc2cf0

tests/fixtures/layouts/single-file-matcher.yaml

@@ -0,0 +1,28 @@
+- pipeline:
+    name: check
+    manager: independent
+    trigger:
+      gerrit:
+        - event: patchset-created
+    success:
+      gerrit:
+        Verified: 1
+    failure:
+      gerrit:
+        Verified: -1
+
+- job:
+    name: base
+    parent: null
+    run: playbooks/base.yaml
+
+- job:
+    name: irr-job
+    irrelevant-files:
+      - README
+
+- project:
+    name: org/project
+    check:
+      jobs:
+        - irr-job