Use a separate console for mounting in root mode.

The normal privileged console mounts emulated storage, which has the
side effect of restricting the mount name space. To avoid this, use a
privileged console without storage mount for mounting purposes.

Patchset 2: Added more situations where new mount console is needed
Patchset 3: Fix line format
Patchset 4: Added suggestion
Patchset 5: Partial revert to PS1

Change-Id: I9372eefa1df91d1ecd3c89a25a391b977d77da45