CLEANUP: conn_stream: apply endp_flags.cocci tree-wide

CLEANUP: conn_stream: apply endp_flags.cocci tree-wide

This changes all main uses of endp->flags to the se_fl_*() equivalent
by applying coccinelle script endp_flags.cocci. The se_fl_*() functions
themselves were manually excluded from the change, of course.

Note: 144 locations were touched, manually reviewed and found to be OK.

The script was applied with all includes:

  spatch --in-place --recursive-includes -I include --sp-file $script $files