Description of problem:
dnf --setopt exclude=XXX adds garbage to excludes; e.g.
dnf update  --setopt exclude='kernel glibc' has [u'kernel', u'glibc', u'k', u'e', u'r', u'n', u'e', u'l', u'g', u'l', u'i', u'b', u'c'] excluded

Version-Release number of selected component (if applicable):
dnf-0.6.3-2.fc21.noarch

How reproducible:
always

Steps to Reproduce:
1. cat <<EOF >>/usr/lib/python2.7/site-packages/dnf-plugins/excludebug.py
from __future__ import absolute_import
from __future__ import unicode_literals

import dnf

class excludebug(dnf.Plugin):
    name = 'repooptionbug'
    def __init__(self, base, cli):
        self.base = base
    def config(self):
        print "self.base.conf.exclude: " , self.base.conf.exclude
EOF

2. dnf update  --setopt exclude='kernel glibc' 
self.base.conf.exclude:  [u'kernel', u'glibc', u'k', u'e', u'r', u'n', u'e', u'l', u'g', u'l', u'i', u'b', u'c']
...


Actual results:
# dnf update  --setopt exclude='kernel glibc' 
self.base.conf.exclude:  [u'kernel', u'glibc', u'k', u'e', u'r', u'n', u'e', u'l', u'g', u'l', u'i', u'b', u'c']
...

Expected results:
# dnf update  --setopt exclude='kernel glibc' 
self.base.conf.exclude:  [u'kernel', u'glibc']


Additional info:
--exclude option seems to be correct:
dnf update  --exclude='kernel glibc' 
self.base.conf.exclude:  [u'kernel', u'glibc']
...