During shutdown, systemd seemingly attempts to unmount each NFS mount twice even though it's no longer mounted at the second try.

Issue

• systemd tries to unmount each NFS mount twice on shutdown even though it's no longer mounted at the second try.

Oct 26 13:50:37 localhost systemd[1]: About to execute: /bin/umount /path/to/the/mount
Oct 26 13:50:37 localhost systemd[1]: Forked /bin/umount as 25793
Oct 26 13:50:37 localhost systemd[1]: path-to-the-mount.mount changed mounted -> unmounting
Oct 26 13:50:37 localhost systemd[1]: Unmounting /path/to/the/mount...
    ...
Oct 26 13:50:37 localhost systemd[25793]: Executing: /bin/umount /path/to/the/mount
    ...
Oct 26 13:50:37 localhost systemd[1]: Child 25793 belongs to path-to-the-mount.mount
Oct 26 13:50:37 localhost systemd[1]: path-to-the-mount.mount mount process exited, code=exited status=0
Oct 26 13:50:37 localhost systemd[1]: path-to-the-mount.mount: mount still present, trying again.
                                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                    　　　　                       　　　　\-----> systemd finds the NFS mount still exists.
    ...
Oct 26 13:50:37 localhost systemd[1]: About to execute: /bin/umount /path/to/the/mount
Oct 26 13:50:37 localhost systemd[1]: Forked /bin/umount as 25821
    ...
Oct 26 13:50:37 localhost systemd[25821]: Executing: /bin/umount /path/to/the/mount 
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                                               \-----> This is the 2nd try to unmount the same NFS mount.
Oct 26 13:50:37 localhost umount[25821]: umount: /path/to/the/mount: not mounted 
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                                               \-----> But it is no longer mounted.
    ...
Oct 26 13:50:37 localhost systemd[1]: Child 25821 (umount) died (code=exited, status=32/n/a)
Oct 26 13:50:37 localhost systemd[1]: Child 25821 belongs to path-to-the-mount.mount
Oct 26 13:50:37 localhost systemd[1]: path-to-the-mount.mount mount process exited, code=exited status=32
Oct 26 13:50:37 localhost systemd[1]: path-to-the-mount.mount changed unmounting -> failed
Oct 26 13:50:37 localhost systemd[1]: Job path-to-the-mount.mount/stop finished, result=done
Oct 26 13:50:37 localhost systemd[1]: Unmounted /path/to/the/mount.
Oct 26 13:50:37 localhost systemd[1]: Unit path-to-the-mount.mount entered failed state.
                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                                           \-----> Accordingly the unit for that mount enters failed state.