host: Don't run nsumount without mountpoints
host: Don't run nsumount without mountpoints

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>

rikur/flynn,flynn/flynn,benbjohnson/flynn,lmars/flynn,philiplb/flynn,benbjohnson/flynn,philiplb/flynn,rikur/flynn,philiplb/flynn,flynn/flynn,lmars/flynn,lmars/flynn,benbjohnson/flynn,philiplb/flynn,rikur/flynn,flynn/flynn,lmars/flynn,rikur/flynn,benbjohnson/flynn,lmars/flynn,rikur/flynn,philiplb/flynn,benbjohnson/flynn,flynn/flynn,rikur/flynn,benbjohnson/flynn,flynn/flynn