audio/avdtp: Fix memory leak

Fixes not freeing the stream if endpoint response with an error
causing the followin trace:

146 (104 direct, 42 indirect) bytes in 1 blocks are definitely lost in loss record 209 of 244
   at 0x4C2A988: calloc (vg_replace_malloc.c:711)
   by 0x50CE580: g_malloc0 (in /usr/lib64/libglib-2.0.so.0.4600.2)
   by 0x42600F: avdtp_setconf_cmd (avdtp.c:1474)
   by 0x42600F: avdtp_parse_cmd (avdtp.c:1966)
   by 0x42600F: session_cb (avdtp.c:2165)
   by 0x50C8E59: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.4600.2)
   by 0x50C91EF: ??? (in /usr/lib64/libglib-2.0.so.0.4600.2)
   by 0x50C9511: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.4600.2)
   by 0x40BFC8: main (main.c:687)
1 file changed