kmshttpendpoint: remove unneded locks.
kmshttpendpoint: remove unneded locks.

function kms_change_internal_pipeline_state is always called with mutex held.

Change-Id: I670c9555b04bd16cfe383503994ac47411e09a12

shelsonjava/kms-core,Kurento/kms-core,ESTOS/kms-core,KurentoLegacy/gst-kurento-plugins,TribeMedia/kms-core,ESTOS/kms-core,TribeMedia/kms-core,Kurento/kms-core,shelsonjava/kms-core,Kurento/kms-core,KurentoLegacy/gst-kurento-plugins,TribeMedia/kms-core,ESTOS/kms-core,shelsonjava/kms-core,KurentoLegacy/gst-kurento-plugins,TribeMedia/kms-core,shelsonjava/kms-core,Kurento/kms-core,ESTOS/kms-core,KurentoLegacy/gst-kurento-plugins