DO NOT MERGE: add interim startDream api.

DreamManager#startDream has been updated on QPR and master which removes
the unnecessary component name parameter, but it breaks TM CTS tests.
The interim api added in this change will prevent breakage on TM, and
should not be merged downstream.

Test: atest DreamManagerServiceTests
Fix: 245223722
Fix: 245058392
Fix: 245070240
Change-Id: Id9e8cc67003da9fc3e03bffd6ec50643d10652b5