TT#28952 Remove 'chroot umount -a'

There is no any source of mount info (mtab or /proc fs) so this
call is useless. Moreover due to absence of mount info it can catch
segfault:
117e8f0763

Change-Id: I0defcc8e6cb25c3534fef1f0281291c07e02f2d5

templates/scripts/includes/deployment.sh

@@ -2465,7 +2465,6 @@ umount ${TARGET}/proc       2>/dev/null || true
 umount ${TARGET}/sys        2>/dev/null || true
 umount ${TARGET}/dev/pts    2>/dev/null || true
 umount ${TARGET}/dev        2>/dev/null || true
-chroot ${TARGET} umount -a  2>/dev/null || true
 sync
 
 # unmount chroot - what else?