Description of problem:

If one tries to update locked module, the "Error: No such module" is displayed, which is not true.

Version-Release number of selected component (if applicable):
dnf-2.6.5-1.git.102.e0caca2.fc27.noarch

How reproducible:
always

Steps to Reproduce:
>> dnf module lock httpd
Loading repositories.
Last metadata expiration check: 2:37:09 ago on Thu 28 Sep 2017 06:11:14 AM UTC.
'httpd' is locked (stream: master, version: 20170905144343)

>> dnf module list --installed | grep httpd 
httpd           master (default) 20170905144343 (locked)                                 default   httpd module   
                              
>> dnf module update httpd
Loading repositories.
Last metadata expiration check: 2:41:56 ago on Thu 28 Sep 2017 06:11:14 AM UTC.
Error: No such module: httpd

>> dnf module list --installed | grep httpd
httpd           master (default) 20170905144343 (locked)                                 default   httpd module  

Expected results:
I believe a message similar to "Module <name> is locked and can't be updated" will be more realistic.