Settings: fix com.android.settings occurs Dalvik leak and Native leak

Duplicate add DataSaverBackend listener when execution onDetached.

Use remove listener to replace add listener to avoid Dalvik leak
and Native leak.
Need to the check if the view is null to avoid Settings crash.

Change-Id: I0a7769a3fc29e88babead23fe0746b32508e2436
CRs-Fixed: 1083427