ApacheHttpClientConnectionHandler: openConnection should be synchronized, should be thread safe and support connection pooling

I found the following issues when using ApacheHttpClientConnectionHandler:
a.) openConnection() should be synchronized. It need not be synchronized if the httpClient was passed in, but that is typically not the case
b.) ApacheHttpClientConnectionHandler should be thread safe and support connection pooling
c.) Deprecated method usage
d.) Request not properly aborted when exceptions are thrown by httpClient#execute()

I will attach a patch. Please review and apply the patch. Thanks