MULE-6908: Property place holders should be supported in test conectivity

    _ Fixing build implementing new method in test callbacks
    (cherry picked from commit da829fcd6b701664efb27e8ba47ab7143ca28ee6)
    _ Avoid null pointer when environment proeprties are null
    (cherry picked from commit dd4e614db699adb3e1f0d3a03cae8dc03d84c0dd)
    _ Fixing MULE-6908
    (cherry picked from commit fd17b7c34b312fddfb16ccdd3c296d805e4273a0)