AVRCP: Fix not freeing session list on exit

AVRCP: Fix not freeing session list on exit

96 (16 direct, 80 indirect) bytes in 1 blocks are definitely lost in loss record 261 of 338
   at 0x4A0884D: malloc (vg_replace_malloc.c:263)
   by 0x4C803FE: g_malloc (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x4C94801: g_slice_alloc (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x4C95B42: g_slist_append (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x12FDAD: state_changed (avrcp.c:1401)
   by 0x12D3B1: avctp_set_state (avctp.c:406)
   by 0x12E5C4: avctp_confirm_cb (avctp.c:896)
   by 0x1607D3: server_cb (btio.c:254)
   by 0x4C7A824: g_main_context_dispatch (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x4C7AB57: ??? (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x4C7AF51: g_main_loop_run (in /usr/lib64/libglib-2.0.so.0.3200.4)
   by 0x120EB1: main (main.c:551)