Merge from @xiaolu: Add exfat for modules or static mode

If you cannot write to partitions, it could be you miss SE permissions

Change-Id: I82f8e72a836d9469412e88e25e9cc2067efcb0ab
Exfat: Mount external volumes with forced context

Change-Id: Iaf3aa0d3635ae5e6b29a208a9493baf76fe58c4f