Enable proguard on service-connectivity

The current proguard rules keep all classes currently in the jar, so
this does not strip any classes, but it applies optimizations on the
code.
Enabling proguard will be useful when adding service-nearby to the jar.

Bug: 189355156
Test: m service-connectivity; check list of classes in jar unchanged
Change-Id: I3be9422a431a5b5bc1478960ce332a89377bd632
2 files changed