88e531f38c
When an automounted filesystem is successfully unmounted, call rpc.umntall(8) with the -k flag. rpc.umntall(8) is used to clean up /var/db/mounttab on the client and /var/db/mountdtab on the server. This is only useful for NFSv3. PR: 251906 Reviewed by: trasz Differential Revision: https://reviews.freebsd.org/D27801