tox: Fix warnings reported by PyLint

fritzcollectd.py:27: [C0411(wrong-import-order), ]
    third party import "import fritzconnection" should be placed before
    "import collectd"
fritzcollectd.py:29: [C0411(wrong-import-order), ]
    third party import "from lxml.etree import XMLSyntaxError" should
    be placed before "import collectd"

fritzcollectd.py

@@ -23,11 +23,12 @@
 
 from collections import namedtuple, OrderedDict
 
-import collectd  # pylint: disable=import-error
 import fritzconnection
 
 from lxml.etree import XMLSyntaxError  # pylint: disable=no-name-in-module
 
+import collectd  # pylint: disable=import-error
+
 __version__ = '0.5.0'