keystore: fix import as other UIDs

The targetUid was not being used as the user to store the key as, so it
was ending up under the calling UID. This change matches the code for
insert and generate now.

Bug: 8634328
Change-Id: Iedbbdaa0ac77f3aedb32a719458b5b503a66efd5

keystore/keystore.cpp

@@ -1727,7 +1727,7 @@ public:
         }
 
         String8 name8(name);
-        String8 filename(mKeyStore->getKeyNameForUidWithDir(name8, callingUid));
+        String8 filename(mKeyStore->getKeyNameForUidWithDir(name8, targetUid));
 
         return mKeyStore->importKey(data, length, filename.string(), callingUid, flags);
     }