pipesz: merge help/version getopt loop into main loop

pipesz: merge help/version getopt loop into main loop

The main() function scanned command-line options in two passes: the
first pass checked for --help/--version, and the second processed
normal options. When getopt_long encountered an unknown option in the
first pass, it printed an error message. The same error was then
printed again during the second pass, resulting in a duplicate
"unrecognized option" message.

Fix this by merging the first getopt_long loop into the main one,
following the standard util-linux convention.

Fixes: https://github.com/util-linux/util-linux/issues/3817
Signed-off-by: Karel Zak <kzak@redhat.com>