init-live.sh: avoid duplicate mount points for the same filesystem

init-live.sh: avoid duplicate mount points for the same filesystem

A live system had duplicate mount points for the same filesystem
in the output of 'mount' command. That was because we didn't handle
the temporary mounts properly before switch_root.

This patch fixes this problem by moving the mount points of some
filesystems to the corresponding directories in the real root filesystem.

[YOCTO #3155]

(From OE-Core rev: 050a745413f8bb26212b84da391e0f7665f77728)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>