Description of problem:

If no package specified with dnf module enable/disable

1) there is no error message. I expect "Package is not specified" and a help/usage page maybe
2) wrong exit status for dnf module disable when no package

[vagrant@fvagrant ~]$ docker exec boltron_container bash -l -c "dnf module disable; echo $?" 
Last metadata expiration check: 16:42:39 ago on Mon Jul 24 16:26:41 2017.
0

[vagrant@fvagrant ~]$ docker exec boltron_container bash -l -c "dnf module enable; echo $?" 
Last metadata expiration check: 16:17:48 ago on Mon Jul 24 16:26:41 2017.
1

Version-Release number of selected component (if applicable):
latest boltron compose 07-17
dnf-2.6.0-3.git.40.c0f7fc6.module_a7788b02.noarch

How reproducible:
always