gerrit: cast change and patchset numbers to str

This is a follow-up to https://review.openstack.org/433748
where we need to cast all json access to change and patchset number
as str. At least the refresh_deps logic relies on python eq check,
and Zuul doesn't dequeue child changes when parent change get
updated in Gerrit-2.14.

Here is diagnostic DEBUG informations
(2 depends-on 1, patchset 1,13 doesn't dequeue change 2):

Change <Change 1,13> is a new version of <Change 1,12>,
  removing <QueueItem for <Change 1,12> in check>
Canceling builds behind change: <Change 1,12> because it is being removed.
Cancel jobs for change <Change 1,12>
Removing change <Change 1,12> from queue
[snip]
Starting queue processor: check
Checking for changes needed by <Change 2,5>:
  Change <Change 2,5> needs change <Change 1,12>:
  Needed change is already ahead in the queue

Change-Id: Id73a479d155fa6d9b2c562869cae6c82dd065911

1 files changed, 2 insertions, 1 deletions

diff --git a/zuul/driver/gerrit/gerritsource.py b/zuul/driver/gerrit/gerritsource.py
index 5927a82b0..c37d74249 100644
--- a/zuul/driver/gerrit/gerritsource.py
+++ b/zuul/driver/gerrit/gerritsource.py
@@ -97,7 +97,8 @@ class GerritSource(BaseSource):
                         break
                 if not found:
                     continue
-                key = (result['number'], result['currentPatchSet']['number'])
+                key = (str(result['number']),
+                       str(result['currentPatchSet']['number']))
                 if key in seen:
                     continue
                 seen.add(key)