Modify RO mount test to check different processes

Different processes can have their own mount namespaces,
so just because something is mounted read-only in one
process, doesn't mean it's mounted read-only in another
process.

Add a check to init, to see if it mounted /system read-only.

Change-Id: Idf42488060a52fdc1cba06b0788abe740c024e7d
1 file changed