Seek test is waiting for src element to change state. The src element is a
bin containing a fakesouphttpsrc element and a queue2 element. Instead of
waiting for the fakesouphttpsrc element to change state, the test should
wait for the bin to change state (meaning both fakesouphttpsrc and the queue2
element had changed state). This avoids race condition situations when
fakehttpsrc changed state and the test thinks the src has stopped, but
queue2 is still transmitting.