crypto: fix leak in ivgen essiv init

On error path, the 'salt' doesn't been freed thus leading
a memory leak. This patch avoid this.

Signed-off-by: Li Qiang <liqiang6-s@360.cn>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

crypto/ivgen-essiv.c

@@ -48,6 +48,7 @@ static int qcrypto_ivgen_essiv_init(QCryptoIVGen *ivgen,
                            &salt, &nhash,
                            errp) < 0) {
         g_free(essiv);
+        g_free(salt);
         return -1;
     }