MINOR: http-ana: Properly set message flags from the start-line flags

MINOR: http-ana: Properly set message flags from the start-line flags

CNT_LEN and TE_CHNK flags must be set on the message only when the
corresponding flag is set on the HTX start-line. Before, when the transfer
length was known XFER_LEN set), the HTTP_MSGF_TE_CHNK was the default. But
it is not appropriate. Now, it is only set if the message is chunked. Thus,
it is now possible to have a known transfer length without CNT_LEN or
TE_CHNK.

In addition, the BODYLESS flags may be set, independently on XFER_LEN one.