gst/playback/: More fixes on reusing of the element.
gst/playback/: More fixes on reusing of the element.

Original commit message from CVS:
* gst/playback/gstdecodebin.c: (gst_decode_bin_get_type),
(gst_decode_bin_class_init), (gst_decode_bin_factory_filter),
(compare_ranks), (print_feature), (gst_decode_bin_init),
(gst_decode_bin_dispose), (find_compatibles), (close_pad_link),
(try_to_link_1), (new_pad), (close_link), (type_found),
(gst_decode_bin_set_property), (gst_decode_bin_get_property),
(gst_decode_bin_change_state), (plugin_init):
* gst/playback/gstplaybasebin.c: (gst_play_base_bin_get_type),
(gst_play_base_bin_class_init), (gst_play_base_bin_init),
(gst_play_base_bin_dispose), (queue_overrun),
(gen_preroll_element), (remove_prerolls), (no_more_pads),
(new_stream), (setup_source), (gst_play_base_bin_set_property),
(gst_play_base_bin_get_property), (play_base_eos),
(gst_play_base_bin_change_state), (gst_play_base_bin_add_element),
(gst_play_base_bin_remove_element),
(gst_play_base_bin_mute_stream), (gst_play_base_bin_link_stream),
(gst_play_base_bin_unlink_stream),
(gst_play_base_bin_get_streaminfo):
* gst/playback/gstplaybasebin.h:
* gst/playback/gstplaybin.c: (gst_play_bin_get_type),
(gst_play_bin_class_init), (gst_play_bin_init),
(gst_play_bin_dispose), (gst_play_bin_set_property),
(gst_play_bin_get_property), (gen_video_element),
(gen_audio_element), (remove_sinks), (setup_sinks),
(gst_play_bin_change_state), (gst_play_bin_get_event_masks),
(gst_play_bin_send_event), (gst_play_bin_get_formats),
(gst_play_bin_convert), (gst_play_bin_get_query_types),
(gst_play_bin_query), (plugin_init):
* gst/playback/test4.c: (main):
More fixes on reusing of the element.

veo-labs/gst-plugins-good,roopar/gst-plugins-good,hizukiayaka/gst-plugins-good,chamois94/gst-plugins-good,cfoch/gst-plugins-good,Kurento/gst-plugins-good,greg80303/gst-plugins-good,luisbg/gst-plugins-good,davibe/gst-plugins-good-1.0,Kurento/gst-plugins-good,cablelabs/gst-plugins-good,BigBrother-International/gst-plugins-good,froggatt/gst-plugins-good-m,GrokImageCompression/gst-plugins-good,surround-io/gst-plugins-good,ahmedammar/platform_external_gst_plugins_good,pexip/gst-plugins-good,greg80303/gst-plugins-good,cablelabs/gst-plugins-good,krieger-od/gst-plugins-good,jahrome/gst-plugins-good,reynaldo-samsung/gst-plugins-good,krieger-od/gst-plugins-good,davibe/gst-plugins-good-1.0,cfoch/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,Distrotech/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,davibe/gst-plugins-good-1.0,GrokImageCompression/gst-plugins-good,shelsonjava/gst-plugins-good,alessandrod/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,matsu/gst-plugins-good,stfl/gst-plugins-good,knuesel/gst-plugins-good,offlinehacker/gst-plugins-good,collects/gst-plugins-good,reynaldo-samsung/gst-plugins-good,an146/gst-plugins-good,veo-labs/gst-plugins-good,pexip/gst-plugins-good,sebras/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,an146/gst-plugins-good,jahrome/gst-plugins-good,pexip/gst-plugins-good,krad-radio/gstreamer-plugins-good-krad,shelsonjava/gst-plugins-good,jcaden/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,jhodapp/gst-plugins-good,Kurento/gst-plugins-good,strukturag/gst-plugins-good,vatavuserban/gst-plugins-good,rikaunite/gst-opera_gst-plugins-good,knuesel/gst-plugins-good,Distrotech/gst-plugins-good,collects/gst-plugins-good,mrchapp/gst-plugins-good,greg80303/gst-plugins-good,hizukiayaka/gst-plugins-good,roopar/gst-plugins-good,surround-io/gst-plugins-good,veo-labs/gst-plugins-good,mrchapp/gst-plugins-good,luisbg/gst-plugins-good,davibe/gst-plugins-good,rawoul/gst-plugins-good,davibe/gst-plugins-good,GStreamer/gst-plugins-good,PPCDroid/external-gst-plugins-good,roopar/gst-plugins-good,veo-labs/gst-plugins-good,rawoul/gst-plugins-good,cablelabs/gst-plugins-good,ylatuya/gst-plugins-good,froggatt/gst-plugins-good-m,collects/gst-plugins-good,wkatsak/gst-plugins-good,froggatt/gst-plugins-good-m,ted-n/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,hizukiayaka/gst-plugins-good,jpakkane/gstreamer-plugins-good,dgerlach/gst-plugins-good,krad-radio/gstreamer-plugins-good-krad,vatavuserban/gst-plugins-good,loshca/gst-plugins-good,sebras/gst-plugins-good,shelsonjava/gst-plugins-good,shelsonjava/gst-plugins-good,ikonst/gst-plugins-good,sh0/gst-plugins-good,dgerlach/gst-plugins-good,kittee/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,ndufresne/gst-plugins-good,Lachann/gst-plugins-good,froggatt/gst-plugins-good-m,rikaunite/gst-opera_gst-plugins-good,davibe/gst-plugins-good-1.0,zaheerm/gst-plugins-good,surround-io/gst-plugins-good,kittee/gst-plugins-good,strukturag/gst-plugins-good,lovebug356/gst-plugins-good,StreamUtils/gst-plugins-good,ted-n/gst-plugins-good,jcaden/gst-plugins-good,strukturag/gst-plugins-good,sebras/gst-plugins-good,jpakkane/gstreamer-plugins-good,stfl/gst-plugins-good,ariscop/gst-plugins-good,ted-n/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,sebras/gst-plugins-good,davibe/gst-plugins-good,PPCDroid/external-gst-plugins-good,Lachann/gst-plugins-good,PPCDroid/external-gst-plugins-good,krieger-od/gst-plugins-good,ndufresne/gst-plugins-good,offlinehacker/gst-plugins-good,ndufresne/gst-plugins-good,prajnashi/gst-plugins-good,dgerlach/gst-plugins-good,loshca/gst-plugins-good,greg80303/gst-plugins-good,BigBrother-International/gst-plugins-good,Lachann/gst-plugins-good,ahmedammar/platform_external_gst_plugins_good,StreamUtils/gst-plugins-good,jcaden/gst-plugins-good,Lachann/gst-plugins-good,rikaunite/gst-opera_gst-plugins-good,kittee/gst-plugins-good,pexip/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,jpakkane/gstreamer-plugins-good,GrokImageCompression/gst-plugins-good,jpakkane/gstreamer-plugins-good,Kurento/gst-plugins-good,ikonst/gst-plugins-good,alessandrod/gst-plugins-good,ikonst/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,vatavuserban/gst-plugins-good,alessandrod/gst-plugins-good,ylatuya/gst-plugins-good,vatavuserban/gst-plugins-good,hizukiayaka/gst-plugins-good,rikaunite/gst-opera_gst-plugins-good,ariscop/gst-plugins-good,surround-io/gst-plugins-good,ylatuya/gst-plugins-good,jhodapp/gst-plugins-good,prajnashi/gst-plugins-good,chamois94/gst-plugins-good,mrchapp/gst-plugins-good,kittee/gst-plugins-good,Distrotech/gst-plugins-good,wkatsak/gst-plugins-good,knuesel/gst-plugins-good,an146/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,chamois94/gst-plugins-good,zaheerm/gst-plugins-good,ylatuya/gst-plugins-good,jhodapp/gst-plugins-good,collects/gst-plugins-good,BigBrother-International/gst-plugins-good,jhodapp/gst-plugins-good,cfoch/gst-plugins-good,ndufresne/gst-plugins-good,Distrotech/gst-plugins-good,stfl/gst-plugins-good,wkatsak/gst-plugins-good,luisbg/gst-plugins-good,zaheerm/gst-plugins-good,ahmedammar/platform_external_gst_plugins_good,ted-n/gst-plugins-good,offlinehacker/gst-plugins-good,an146/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,mrchapp/gst-plugins-good,wkatsak/gst-plugins-good,matsu/gst-plugins-good,ariscop/gst-plugins-good,Distrotech/gst-plugins-good,pexip/gst-plugins-good,lovebug356/gst-plugins-good,ikonst/gst-plugins-good,lovebug356/gst-plugins-good,offlinehacker/gst-plugins-good,ahmedammar/platform_external_gst_plugins_good,loshca/gst-plugins-good,luisbg/gst-plugins-good,matsu/gst-plugins-good,jahrome/gst-plugins-good,mrchapp/gst-plugins-good,krad-radio/gstreamer-plugins-good-krad,knuesel/gst-plugins-good,sh0/gst-plugins-good,zaheerm/gst-plugins-good,GStreamer/gst-plugins-good,StreamUtils/gst-plugins-good,Kurento/gst-plugins-good,stfl/gst-plugins-good,BigBrother-International/gst-plugins-good,jahrome/gst-plugins-good,rawoul/gst-plugins-good,sh0/gst-plugins-good,lovebug356/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer-sdk__gst-plugins-good,cablelabs/gst-plugins-good,reynaldo-samsung/gst-plugins-good,jcaden/gst-plugins-good,alessandrod/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,reynaldo-samsung/gst-plugins-good,krad-radio/gstreamer-plugins-good-krad,prajnashi/gst-plugins-good,rawoul/gst-plugins-good,strukturag/gst-plugins-good,krieger-od/gst-plugins-good,loshca/gst-plugins-good,cfoch/gst-plugins-good,matsu/gst-plugins-good,chamois94/gst-plugins-good,ariscop/gst-plugins-good,sh0/gst-plugins-good