rpki-client: plug leak of crldp in mft_parse()

[Theo Buehler]

If the checks involving crlfile fail one way or the other, we'll leak
crldp. Here's one way to fix it.  We could also drop the free(crldp) in
the body or add a free to the relevant conditional.

Index: mft.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/mft.c,v
retrieving revision 1.58
diff -u -p -r1.58 mft.c
--- mft.c       19 Apr 2022 09:52:29 -0000      1.58
+++ mft.c       19 Apr 2022 18:15:49 -0000
@@ -446,7 +446,7 @@ mft_parse(X509 **x509, const char *fn, c
        int              rc = 0;
        size_t           cmsz;
        unsigned char   *cms;
-       char            *crldp, *crlfile;
+       char            *crldp = NULL, *crlfile;
 
        memset(&p, 0, sizeof(struct parse));
        p.fn = fn;
@@ -489,6 +489,7 @@ mft_parse(X509 **x509, const char *fn, c
        if ((p.res->crl = strdup(crlfile + 1)) == NULL)
                err(1, NULL);
        free(crldp);
+       crldp = NULL;
 
        if (mft_parse_econtent(cms, cmsz, &p) == 0)
                goto out;
@@ -501,6 +502,7 @@ out:
                X509_free(*x509);
                *x509 = NULL;
        }
+       free(crldp);
        free(cms);
        return p.res;
 }