libf2fs: check more conditions on mounted filesystem

In the case of lazy umount, "umount -l", some processes are able to use the
file system even if its mountpoint was disconnected.
At this moment, we should not allow mkfs.f2fs.
This patch adds this condition check.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
4 files changed