MT#55283 codec_add_raw_packet_dup: allocate enough space to support encrpytion
using str_init_dup_str doesn't leave enough room for appending encryption
related pieces to the end of the packet when used for, eg, dtmf
injection
closes#1819
Change-Id: Iefae0e04b38f4a3eaaac32ed1ba70c7e3ee8e979