Group endpoint support for call and callout Mediators in blocking mode

[abeykoon]

Description:

Currently call mediator in blocking mode does not support group endpoints. Namely, group endpoints are

1. Failover EP
2. Loadbalance EP
3. Recipient list EP

Here we need to do the calling in the same thread. As Recipient list EP sends clones of the message to all the leaf endpoints specified, it is bit complicated. Hence considering the usecases it is enough to implement the feature for Failover and Loadbalance EPs.

Affected Product Version:

EI 6.1.1

OS, DB, other environment details and versions:

Java 8

Steps to reproduce:

N/A

Related Issues:
Related PR:
https://github.com/wso2/wso2-synapse/pull/836/files