Don't print the packet counter when capturing if we're also printing
packet information to a terminal (which we assume is the same terminal
as the one to which the packet counts are being printed), as they get in
the way of each other.

Don't print it if we're sending the standard error to a terminal, or if
-q is specified, either.

Put all the setting of print_packet_counts together; it looks as if the
default value of print_packet_counts may have been changed to TRUE and
the code to handle -q wasn't changed to set it to FALSE if -q was
specified rather than setting it to TRUE if it wasn't specified.

Change-Id: Ifa8fd70c1694235f0ee8cd0e52eb860286329138
Reviewed-on: https://code.wireshark.org/review/3951
Reviewed-by: Guy Harris <guy@alum.mit.edu>