Give migrations tests more time to run

Migrations tests usually take longer to run that most other
tests. Increase the time out value just for migrations tests,
so that we don't hit various time out errors running unit tests
when CI test nodes slow down a bit.

Closes-Bug: #1216851

Change-Id: I48d7c125397cd282d52eb8e1a1ccb699188d8f14
Merge "Give migrations tests more time to run"