kmsbasertpendpoint: implement base set_transport_to_sdp

Code moved from kmswebrtcendpoint

Change-Id: I28d47fb8c8dedc2e29729671319d191c3c5d55ff
kmsbasertpendpoint: improve getting lock for properties getter/setter

Change-Id: Ied08a76c007211d8f1163e92b81f614df08bf7af
kmsbasertpendpoint: use bundle property

This can be useful for child classes

Change-Id: I629fa30e723288669ef4898b4305cf55e5d689d4
kmsbasertpendpoint: get ssrc form RtpSession

Change-Id: Ic286590d652c9eabdbf4be398ff7113563475288