p2p/protocols: fix data race in TestProtocolHook (#19242)

dummyHook's fields were concurrently written by nodes and read by
the test. The simplest solution is to protect all fields with a mutex.

Enable: TestMultiplePeersDropSelf, TestMultiplePeersDropOther as they
seemingly accidentally stayed disabled during a refactor/rewrite
since 1836366ac1.

resolves ethersphere/go-ethereum#1286

p2p/protocols/accounting_simulation_test.go

@@ -161,7 +161,7 @@ func TestAccountingSimulation(t *testing.T) {
 type matrix struct {
 	n    int     //number of nodes
 	m    []int64 //array of balances
-	lock sync.RWMutex
+	lock sync.Mutex
 }
 
 // create a new matrix