x509.c: Fix potential memory leak in X.509 self test

Found and fixed by Junhwan Park in #2106.

Signed-off-by: Junhwan Park <semoking@naver.com>
diff --git a/library/x509.c b/library/x509.c
index 52b5b64..7cc813e 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -1001,8 +1001,8 @@
  */
 int mbedtls_x509_self_test( int verbose )
 {
+    int ret = 0;
 #if defined(MBEDTLS_CERTS_C) && defined(MBEDTLS_SHA256_C)
-    int ret;
     uint32_t flags;
     mbedtls_x509_crt cacert;
     mbedtls_x509_crt clicert;
@@ -1010,6 +1010,7 @@
     if( verbose != 0 )
         mbedtls_printf( "  X.509 certificate load: " );
 
+    mbedtls_x509_crt_init( &cacert );
     mbedtls_x509_crt_init( &clicert );
 
     ret = mbedtls_x509_crt_parse( &clicert, (const unsigned char *) mbedtls_test_cli_crt,
@@ -1019,11 +1020,9 @@
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( ret );
+        goto cleanup;
     }
 
-    mbedtls_x509_crt_init( &cacert );
-
     ret = mbedtls_x509_crt_parse( &cacert, (const unsigned char *) mbedtls_test_ca_crt,
                           mbedtls_test_ca_crt_len );
     if( ret != 0 )
@@ -1031,7 +1030,7 @@
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( ret );
+        goto cleanup;
     }
 
     if( verbose != 0 )
@@ -1043,20 +1042,19 @@
         if( verbose != 0 )
             mbedtls_printf( "failed\n" );
 
-        return( ret );
+        goto cleanup;
     }
 
     if( verbose != 0 )
         mbedtls_printf( "passed\n\n");
 
+cleanup:
     mbedtls_x509_crt_free( &cacert  );
     mbedtls_x509_crt_free( &clicert );
-
-    return( 0 );
 #else
     ((void) verbose);
-    return( 0 );
 #endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA1_C */
+    return( ret );
 }
 
 #endif /* MBEDTLS_SELF_TEST */