nicer rpki-client -V output

[Claudio Jeker]

Lets print the version string a bit nicer.
Instead of
        rpki-client: version: 7.0
print
        rpki-client 7.0

OK?
-- 
:wq Claudio

Index: main.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/main.c,v
retrieving revision 1.135
diff -u -p -r1.135 main.c
--- main.c      11 Apr 2021 01:20:03 -0000      1.135
+++ main.c      13 Apr 2021 19:49:24 -0000
@@ -674,7 +674,8 @@ main(int argc, char *argv[])
                        verbose++;
                        break;
                case 'V':
-                       errx(0, "version: %s", RPKI_VERSION);
+                       fprintf(stderr, "rpki-client %s\n", rpki_version);
+                       return 0;
                default:
                        goto usage;
                }