Fix KCM key mapping cloning

ag/23792288 tried to fix a security issue by cloning the key
mappings, but unfortunately the parcel was not being rewinded.

Bug: 274058082
Test: Confirmed change works in newer Android versions
Merged-In: I745008a0a8ea30830660c45dcebee917b3913d13
Change-Id: I6f75b9202e20d82ebf81a35a2916e653ee1b8372