input-selector: Let context queries pass through

By doing so GL source elements can successfully reuse the GL context and display
of downstream elements. This change fixes an issue in playbin when using
gltestsrc where the context query made by the source element would fail and the
source element would create a second (useless) GLDisplay.
3 jobs for philn/inputselector-context-query in 5 minutes and 57 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Preparation
passed #51991
manifest

00:00:22

 
  Build
passed #51992
build fedora x86_64

00:02:48

 
  Full Builds
passed #51993
build android arm64 api28

00:02:46