transport->progress: use flag authoritatively

transport->progress: use flag authoritatively

Set transport->progress in transport.c::transport_set_verbosity() after
checking for the appropriate conditions (eg. --progress, isatty(2)),
and thereafter use it without having to check again.

The rules used are as follows (processing aborts when a rule is
satisfied):

  1. Report progress, if force_progress is 1 (ie. --progress).
  2. Don't report progress, if verbosity < 0 (ie. -q/--quiet).
  3. Report progress if isatty(2) is 1.

This changes progress reporting behaviour such that if both --progress
and --quiet are specified, progress is reported.

In two areas, the logic to determine whether to *not* show progress is
changed to simply use the negation of transport->progress. This changes
behaviour in some ways (see previous paragraph for details).

Signed-off-by: Tay Ray Chuan <rctay89@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>