Description of problem:
We cannot install packages during registration with AK, when we register dnf-client (F23).

Version-Release number of selected component (if applicable):
dnf-plugin-spacewalk-2.5.3-1.fc23.noarch

How reproducible:
100%

Steps to Reproduce:
1. We have got SW with some synchronized base channel (in my case F23).
2. We create new Activation Key and add package to install (ex. mc or vim-enhanced).
3. Register client to SW via AK
> rhnreg_ks --serverUrl=https://<fqdn>/XMLRPC --activationkey=1-xxx --force -vvv

Actual results:
...
D: do_call packages.update([['vim-enhanced', '', '', '', '']],){'cache_only': None}
D: Called update[['vim-enhanced', '', '', '', '']]
...
D: rpcServer: Calling XMLRPC up2date.listChannels
E: Package vim-enhanced-0:- is not available for installation
D: Sending back response(32, 'Failed: Packages failed to install properly:\nPackage vim-enhanced-0:- is not available for installation', {'name': 'package_install_failure', 'version': '1'})


Expected results:
...
D: do_call packages.update([['vim-enhanced', '', '', '', '']],){'cache_only': None}
D: Called update[['vim-enhanced', '', '', '', '']]
...
D: rpcServer: Calling XMLRPC up2date.listChannels
D: Dependencies Resolved
Downloading and installing: ['gpm-libs-1.20.7-7.fc23.i686', 'vim-filesystem-2:7.4.827-1.fc23.i686', 'vim-enhanced-2:7.4.827-1.fc23.i686', 'vim-common-2:7.4.827-1.fc23.i686']


Additional info:

Fix: https://github.com/spacewalkproject/spacewalk/pull/365