agnosticbin: Wait until tees have been negotiated before use them
agnosticbin: Wait until tees have been negotiated before use them

This fix a concurrency problem while connecting elements

Change-Id: I90d6c2ce2837925359921b50bf3f27a904cf9675

shelsonjava/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements,Kurento/kms-elements,TribeMedia/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,Kurento/kms-elements,Kurento/kms-elements