s3:popt_common: simplify popt_common_credentials handling
This offers a global 'struct user_auth_info *cmdline_auth_info',
similar to the 'cmdline_credentials' we have in
source4/lib/cmdline/popt_common.c.
And we create that in the POPT_CALLBACK_REASON_PRE stage
and finalize it in the POPT_CALLBACK_REASON_POST stage.
That means much less boring work for the callers
and more freedom to change the user_auth_info internals
in future.
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>