libext2fs: Add an explicit error code for missing mtab file

To reduce user confusion, if the /etc/mtab file is missing
ext2fs_check_mount_point and ext2fs_check_if_mounted will return a
new, explicit error code to indicate this case.

Addresses-Debian-Bug: #527859

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2 files changed