[Mobile] flowOn for cdmaRoaming

This flow is often triggered from the main thread, and should be
offloading its call into `telephonyManager`.

Test: all tests in statusbar/pipeline/mobile
Flag: NONE bugfix
Fixes: 328600442
Change-Id: Ib5d42cd0e948488ee39730e85aba4f5f268b1645
1 file changed