tests: extend the AM_TESTS_ENVIRONMENT from check.mak
tests: extend the AM_TESTS_ENVIRONMENT from check.mak

To get the CK_DEFAULT_TIMEOUT defined for all tests

https://bugzilla.gnome.org/show_bug.cgi?id=761472

GrokImageCompression/gst-plugins-ugly,GStreamer/gst-plugins-ugly,Kurento/gst-plugins-ugly,Kurento/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,GStreamer/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,GrokImageCompression/gst-plugins-ugly,GStreamer/gst-plugins-ugly,Kurento/gst-plugins-ugly,StreamUtils/gst-plugins-ugly,StreamUtils/gst-plugins-ugly