Let's think about "mount --onlyonce".
Addresses: https://github.com/karelzak/util-linux/issues/448
Signed-off-by: Karel Zak <kzak@redhat.com>
libmount (mount/umount)
-----------------------
+ - add --onlyonce to force mount(8) to check if mountpoint is already used. Now
+ "already mounted" detection is used for --all only. The problem is if you
+ call "mount <mountpoint>" more than once for in fstab defined tmpfs (or network
+ filesystem etc.). In this case kernel does not return EBUSY, but a new instance
+ of the FS is created. https://github.com/karelzak/util-linux/issues/448
+
- support CAP_SYS_ADMIN; for mount(2) syscall the CAP_SYS_ADMIN is good
enough. Unfortunately, mount(8) does more things like check for filesystem
type (but it's usually done by udev, so root perms are unnecessary), create