Not registering the valve if external api gateway is configured.

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/platform/trunk@179101 a5903396-d722-0410-b921-86c7d4935375
Apply changes related to modification in APIManager config in carbon xml

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/platform/trunk@179102 a5903396-d722-0410-b921-86c7d4935375