Fix StorageManagerService linkToDeath more than one time when vold/storaged died.

Storaged and vold register Binder.linkToDeath in the same method, once one died,
the other would register Binder.linkToDeath many times. Once the other died, it
would receive binderDied callBack many times, then executing volume reset command
many times in very short time, it's a bad user experience.

Bug:135167044
Test:kill vold and storaged, just one time binderDied callBack, so just run one
time volume reset.

Change-Id: I881af5b6ce399dad39274fc2598e92a3b9f88a77