Unlink only volume keys that were previously stored in keyring.

This is only preparation for an extension later, however, the volume
keys should not be unloaded unconditionally from keyring.

Note that all other places dropping keys already check that keys
were uploaded through key ID setting.
(And for suspend unconditional unlink make sense too.)

lib/volumekey.c

@@ -27,6 +27,7 @@ struct volume_key *crypt_alloc_volume_key(size_t keylength, const char *key)
 	vk->key_description = NULL;
 	vk->keyring = INVALID_KEY;
 	vk->keylength = keylength;
+	vk->uploaded = false;
 	vk->id = KEY_NOT_VERIFIED;
 	vk->next = NULL;