Settings: keep the old ringtine cache not delete when set failed.

Delete the ringtone cache after execute setting success.
Fix the ringtone cache is lost case:
Ringtone setting: 1. delete cache; 2. execute setting; 3. cache ringtone
If set the same ringtone as the old setting, it would return after the
2nd step and wouldn't cache again. The cache is lost in this operation.
It would cause there is no cache for playback when CE storage is locked.

Test: atest CtsProviderTestCases -t android.provider.cts.settings

Change-Id: I2bd605450e5116edc0465284242b5daf24ad326a
Signed-off-by: Fang Zhaohui <fangzhaohui@xiaomi.corp-partner.google.com>