LineageStats: explicitly cancel old jobs

* A new job gets scheduled every day or at reboot
* In case an user does not have a network connection, the jobs stack up as per AOSP documentation of setRequiredNetworkType
* We only want to report to the server once, so there is no need to keep old jobs any longer, we therefore cancel the old jobs

Change-Id: I3c6baaf3b10658aa2e49b8ac8d207aa9eac82772