Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/f4370aed91df
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #17593 from bobsilverberg/plivo_call

Bug 924833 - Re-enable test_receive_call.py

========

https://hg.mozilla.org/integration/gaia-central/rev/8732231c56a3
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 924833 - Re-enable test_receive_call.py

Add a step to check that there are credits available for making a call
Add test to manifest

Address code review comments:
- Fail when Plivo balance is insufficient
- Break out arguments to PlivoUtil __init__
- Use marionette.Wait for waiting
- Add a custom PlivoError exception
- General code cleanup

Address pull request comments:
- move check for balance into make_call in the utility class
- address syntax nits
- add custom message to custom exception
- change syntax for custom exceptions

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "a70a7687d22ba838f40e91d8bc3734515e933312", 
+    "revision": "f4370aed91df3bf243fce63085fe7edaca4c5c38", 
     "repo_path": "/integration/gaia-central"
 }