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

_ Managing keep-alive override in endpoint
_ Updating test to check for keep alive in  HTTP 1.0 and 1.1 versions
(cherry picked from commit aa4bbdc)
(cherry picked from commit 92b39be)
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)