qmemmand: separate SystemState init xc and xs to a 'init' method

It prevents any connection to xen when initiallizing the class
notably in doc build generation.

qubes/qmemman/__init__.py

@@ -57,6 +57,10 @@ class SystemState(object):
         self.log.debug('SystemState()')
 
         self.domdict = {}
+        self.xc = None
+        self.xs = None
+
+    def init(self):
         self.xc = xen.lowlevel.xc.xc()
         self.xs = xen.lowlevel.xs.xs()
         self.BALOON_DELAY = 0.1

qubes/tools/qmemmand.py

@@ -276,6 +276,10 @@ def main():
 
     log.debug('instantiating server')
     os.umask(0)
+
+    # Initialize the connection to Xen and to XenStore
+    system_state.init()
+
     server = socketserver.UnixStreamServer(SOCK_PATH, QMemmanReqHandler)
     os.umask(0o077)