kmsplayerendpoint: Modify how to perform the seek
kmsplayerendpoint: Modify how to perform the seek

Modify how to perform the seek and copy how it is done in gst-play

Change-Id: Ice5e390e9745ba301b05fada1a6d32f9a3565d93

Kurento/kms-elements,Kurento/kms-elements,Kurento/kms-elements