am 50717d3c: merge from open-source master

Merge commit '50717d3ca874d13f802e402e43dd9cbd5b19539a'

* commit '50717d3ca874d13f802e402e43dd9cbd5b19539a':
  system/core: vold: Change permission of external storage device nodes
  vold: Check partitions 1-4 instead of 0-3