slapos/slap: Stabilise connection_dict

connection_dict generated by client can be different in details from the
server side, especially it could be directly serialised to string like:

"{u'key': u'value', 'int': 1, 'empty': None}"

So pass it thorugh a way how it is treat on the server, so it would always be:

"{'key': 'value', 'int': '1', 'empty': ''}"

slapos/slap/slap.py

@@ -44,7 +44,7 @@ from functools import wraps
 
 import six
 
-from .util import xml2dict
+from .util import xml2dict, dict2xml
 from .exception import ResourceNotReady, ServerError, NotFoundError, \
           ConnectionError
 from .hateoas import SlapHateoasNavigator, ConnectionHelper
@@ -608,6 +608,8 @@ class ComputerPartition(SlapRequester):
       return self._software_release_document
 
   def setConnectionDict(self, connection_dict, slave_reference=None):
+    # recreate connection_dict that it would became the same as on server
+    connection_dict = xml2dict(dict2xml(connection_dict))
     if self.getConnectionParameterDict() == connection_dict:
       return