Revert "Fix ipv4 netmask error when run slapformat in the Cygwin"

This reverts commit 06ebfdb7.

slapos/format.py

@@ -844,8 +844,8 @@ class Interface(object):
 
   def addIPv4LocalAddress(self, addr=None):
     """Adds local IPv4 address in ipv4_local_network"""
-    netmask = str(netaddr.IPNetwork(self.ipv4_local_network).netmask) \
-              if sys.platform == 'cygwin' else '255.255.255.255'
+    netmask = self.ipv4_local_network if sys.platform == 'cygwin' \
+              else '255.255.255.255'
     local_address_list = self.getIPv4LocalAddressList()
     if addr is None:
       return self._generateRandomIPv4Address(netmask)