build: fix build on recent gcc, DhParams must be destructible

On recent gcc, daemon fails (static assertion failed: result type
must be destructible) cause futures must access the destructor
since commit/71ed3c0c9a3458998bded8e2443c0a680c2eb8cd in gcc

Change-Id: I1e7d35da6aeaffffcb6aa9362d335625ea370052