shout2: Add compatibility for libshout >= 2.4.2 shout_open return values
Fixes gst-plugins-good#848 (closed) In libshout >=2.4.2 shout_open returns SHOUTERR_RETRY instead of SHOUTERR_BUSY. The nonblocking example in libshout, fixes the problem in a similar way, as mentioned by the author in this issue: https://gitlab.xiph.org/xiph/icecast-libshout/-/issues/2316