tune2fs: check whether filesystem is in use for I_flag and Q_flag test

tune2fs: check whether filesystem is in use for I_flag and Q_flag test

For changing inode size (-I) and setting quota fearture (-Q), tune2fs
only check whether the filesystem is umounted. Considering mount
namepspaces, the filesystem is umounted, however it already be left
in other mount namespace.
So we add one check whether the filesystem is not in use with using
EXT2_MF_BUSY flag, which can indicate the device is already opened
with O_EXCL, as suggested by Ted.

Reported-by: Baokun Li <libaokun1@huawei.com>
Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
Link: https://lore.kernel.org/r/28455341-ca26-d203-8b54-792bae002251@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>