expand the check() function to look at filesystem usage
expand the check() function to look at filesystem usage

If the filesystem free blocks goes below the FILESYSTEM_LOWATER call
xfs_growfs to expand the filesystem size.

Signed-off-by: Todd Gill <7afbb5ba98932b8ffb9cc9e6675c4792db142529@redhat.com>

trgill/stratisd,stratis-storage/stratisd,mulkieran/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,trgill/stratisd,mulkieran/stratisd