Explicit Roboletric version for runner

* Our test target uses default roboletric target
(platform-robolectric-prebuilt), which is 3.1.1.
* Runner was updated to 3.4.2 recently (ag/3181301).
* `make RunFrameworksServicesRoboTests` broke because
org.robolectric.res.builder.DefaultPackageManager doesn't exist in new
verion (http://robolectric.org/migrating/#packagemanager-1).

Hardcoded version in our target until we migrate to new version (I tried
but there were some other errors)

Test: make RunFrameworksServicesRoboTests
Change-Id: Ie934dedec3340620611f3d72b75e5eefba430f35