Remove usages of deprecated name LoopingCall in rpc

LoopingCall has been renamed to FixedIntervalLoopingCall
(no functional changes, so a 1:1 replace is just fine)

Closes-Bug: #1307560

Change-Id: Ic8ecf0b57b659446966d7501b8bc49316ff462b0
Merge "Remove usages of deprecated name LoopingCall in rpc"