node_exporter trying to run statfs on Docker files

I installed the nightly build and noticed these error messages from node_exporter:

2017-12-24_16:29:02.13664 time="2017-12-24T16:29:02Z" level=error msg="Error on statfs() system call for \"/run/docker/netns/92950b201cd2\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:17.12845 time="2017-12-24T16:29:17Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/overlay2/6aeee31ac9c8c92d95e31382c59c34282b441866bc00c02ebb74cfda290f3696/merged\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:17.12848 time="2017-12-24T16:29:17Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/containers/614bbf54275a4b2d1fc951f94bd8465fbc5257877e8387b809f2199a83b24fe2/shm\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:17.12848 time="2017-12-24T16:29:17Z" level=error msg="Error on statfs() system call for \"/run/docker/netns/92950b201cd2\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:32.13099 time="2017-12-24T16:29:32Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/overlay2/6aeee31ac9c8c92d95e31382c59c34282b441866bc00c02ebb74cfda290f3696/merged\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:32.13102 time="2017-12-24T16:29:32Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/containers/614bbf54275a4b2d1fc951f94bd8465fbc5257877e8387b809f2199a83b24fe2/shm\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:32.13147 time="2017-12-24T16:29:32Z" level=error msg="Error on statfs() system call for \"/run/docker/netns/92950b201cd2\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:47.13093 time="2017-12-24T16:29:47Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/overlay2/6aeee31ac9c8c92d95e31382c59c34282b441866bc00c02ebb74cfda290f3696/merged\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:47.13154 time="2017-12-24T16:29:47Z" level=error msg="Error on statfs() system call for \"/var/lib/docker/containers/614bbf54275a4b2d1fc951f94bd8465fbc5257877e8387b809f2199a83b24fe2/shm\": permission denied" source="filesystem_linux.go:57"
2017-12-24_16:29:47.13178 time="2017-12-24T16:29:47Z" level=error msg="Error on statfs() system call for \"/run/docker/netns/92950b201cd2\": permission denied" source="filesystem_linux.go:57"

/cc: @bjk-gitlab, @joshlambert