TelephonyTest#waitUntilReady only blocks if mReady is false.

TelephonyTest#waitUntilReady now always waits. But there's a
chance that before it starts, mReady is set to true. In that case,
it will wait for 30 seconds blindly. Making the change so that
it only waits if mReady is false.

Bug: 113305153
Test: unittest
Change-Id: I1072bc86c135769a68d3d10228bed8b050005084