Description of problem:
Using hammer we are restricted to provide some particular arguments for Simplified ACS when we create one. However, we are not restricted to provide the same arguments when we update an existing Simplified ACS. 

In particular, the arguments and validations are:
                        Validation on
Argument                Create  Update
--base-url              ok      X
--subpaths              ok      X
--verify-ssl            X       X
--ssl-ca-cert-id        ok      X
--ssl-client-cert-id    ok      X
--ssl-client-cert-id    ok      X
--upstream-password     ok      X
--upstream-username     ok      X

The purpose of this BZ is to add the validation where missing (see the X in the table above)


Version-Release number of selected component (if applicable):
6.13.0 snap 5


How reproducible:
always


Steps to Reproduce:
1. Have a Satellite with Simplified ACS created
2. Update the ACS using restricted args:
# hammer alternate-content-source update --id 56 --base-url "https://content.example.com/" --subpaths "yums/,files/" --verify-ssl true --ssl-ca-cert-id 1 --ssl-client-cert-id 1 --ssl-client-cert-id 1 --upstream-username "john" --upstream-password "strong"


Actual results:
Alternate Content Source updated.


Expected results:
Could not update the Alternate Content Source.:
  Validation failed: <argument> must be blank