matroskademux: Unlock stream lock after use
matroskademux: Unlock stream lock after use

Stream lock of sink pad was not unlocked after non-updating seek.

Distrotech/gst-plugins-good,Distrotech/gst-plugins-good,Distrotech/gst-plugins-good,Distrotech/gst-plugins-good,Distrotech/gst-plugins-good