refactor mic/chroot.py

Signed-off-by: Gui Chen <gui.chen@intel.com>
refactor mic/chroot.py:global_mounts

describe more clear logic in this function

Signed-off-by: Gui Chen <gui.chen@intel.com>
refactor chrootdir detecting architecture

Signed-off-by: Gui Chen <gui.chen@intel.com>
move savefs to savefs_before_chroot

Signed-off-by: Gui Chen <gui.chen@intel.com>
kill processes inside instroot chroot

when processes forked inside chroot is alive,
mic should kill it first before umount

Signed-off-by: Gui Chen <gui.chen@intel.com>
add lockfile support for mic/chroot.py module

a simple lockfile implementation is added,
and it is supposed to provide an exclusive
locking in the chroot dir

Signed-off-by: Gui Chen <gui.chen@intel.com>