pool: set state to CONNECTING before initializing tcp handle

This garuntees that if hsk_peer_open() fails, that hsk_peer_close()
will call uv_close() before freeing the peer, preventing a race
condition where libuv tries to free the connection handle after
the peer has been destroyed.

src/pool.c

@@ -896,6 +896,8 @@ hsk_peer_open(hsk_peer_t *peer, const hsk_addr_t *addr) {
   assert(peer && addr);
   assert(peer->pool && peer->loop && peer->state == HSK_STATE_DISCONNECTED);
 
+  peer->state = HSK_STATE_CONNECTING;
+
   hsk_pool_t *pool = (hsk_pool_t *)peer->pool;
   uv_loop_t *loop = pool->loop;
 
@@ -927,9 +929,6 @@ hsk_peer_open(hsk_peer_t *peer, const hsk_addr_t *addr) {
     return HSK_EFAILURE;
   }
 
-  peer->state = HSK_STATE_CONNECTING;
-
-
   hsk_peer_t *peerIter, *next;
   uint64_t active = 0;
   for (peerIter = pool->head; peerIter; peerIter = next) {