Fix LUKS1 format if pkbdf benchamr is disabled.

We use minimum iteration for key digest in this case
(the same already used in LUKS2).

Fixes: #478.

src/cryptsetup.c

@@ -983,6 +983,7 @@ static int set_pbkdf_params(struct crypt_device *cd, const char *dev_type)
 
 	if (opt_pbkdf_iterations) {
 		pbkdf.iterations = opt_pbkdf_iterations;
+		pbkdf.time_ms = 0;
 		pbkdf.flags |= CRYPT_PBKDF_NO_BENCHMARK;
 	}