Comment 2 for bug 1587727

StacktraceTop:
 __libc_message (do_abort=2, fmt=0xb75cde28 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
 malloc_printerr (action=<optimized out>, str=0xb75cde98 "double free or corruption (!prev)", ptr=<optimized out>, ar_ptr=0xb7620780 <main_arena>) at malloc.c:5007
 _int_free (av=0xb7620780 <main_arena>, p=<optimized out>, have_lock=0) at malloc.c:3868
 dns_packet_free (p=0x82072e88) at ../src/resolve/resolved-dns-packet.c:177
 dns_packet_unref (p=0x82072e88) at ../src/resolve/resolved-dns-packet.c:189