common: Fix gnupg_wait_processes.
* common/exechelp-posix.c (gnupg_wait_processes): Loop for r_exitcodes even if we already see an error.
The value stored by waitpid for exit code is encoded; It requires
decoded by WEXITSTATUS macro, regardless of an error.
For example, when one of processes is already exited and another is
still running, it resulted wrong value of in r_exitcodes[n].
- Signed-off-by: NIIBE Yutaka <email@example.com>