MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Fixing message loss tests
MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Fixing mule servlet test
MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Cleaning test
MULE-7557: Upgrade Http transport to use HttpClient v4 for improved outbound performance

Work in progress:

_ Cleaning/fixing tests