Revert "Clean up SubMgr#getOpportunisticSubscriptions."

This reverts commit 9569bc70f923127e7884bd7abfe051e0ccd0216a.

Reason for revert: The cl is breaking git_master.
https://android-build.googleplex.com/builds/submitted/5095196/errorprone/latest/view/logs/build_error.log

Change-Id: I534af936b718b2f132473b5b42ea2faabc9382cd
3 files changed