MULE-6783: HTTP inbound keep-alive attribute not overriding the keepAlive attribute of HTTP connector

_ Fixed scanerio when conector has keepAlive=false and endpoint has keepAlive=true. Original test was incorrect in this case.
(cherry picked from commit e2ac84f)
(cherry picked from commit d503031)
(cherry picked from commit 62219d3)
(cherry picked from commit 1664707)