Add port type on port option

According to http://docs.openstack.org/developer/oslo.config/cfg.html
oslo.config can use portType to support the ability to set valid range
on port option values

Closes-Bug: #1488861

Change-Id: Ic4310532f4155ade1706f0bca8df9466665aea97

etc/magnum/magnum.conf.sample

@@ -229,6 +229,8 @@
 #
 
 # The port for the Magnum API server. (integer value)
+# Minimum value: 1
+# Maximum value: 65535
 #port = 9511
 
 # The listen IP for the Magnum API server. (string value)
@@ -703,6 +705,8 @@
 #k8s_protocol = http
 
 # Default port of the k8s master endpoint. (integer value)
+# Minimum value: 1
+# Maximum value: 65535
 #k8s_port = 8080