[DROID] Read /proc/mounts in one go to avoid race.

/proc/mounts is only guaranteed atomic for the current read operation.
[DROID] Only add one mount point per device

I've observed some prettys strange behavior on AML devices regarding
reading /proc/mounts.  Somehow there are multiple, unique mount points
for some devices when reading /proc/mounts with fopen/fgets.  However
they don't exist if "cat /proc/mounts" is issued from the shell.
Baffling...