Register forgotten metrics (#4653)

Follow-up from #4606, where I forgot to register some metrics, whoops.

ca/ca.go

@@ -296,6 +296,7 @@ func NewCertificateAuthorityImpl(
 		Name: "signature_errors",
 		Help: "A counter of signature errors labelled by error type",
 	}, []string{"type"})
+	stats.MustRegister(signErrorCounter)
 
 	ca = &CertificateAuthorityImpl{
 		sa:                 sa,

cmd/ocsp-updater/main.go

@@ -133,6 +133,7 @@ func newUpdater(
 		Name: "ocsp_updater_ticks",
 		Help: "A histogram of ocsp-updater tick latencies labelled by result",
 	}, []string{"result", "long"})
+	stats.MustRegister(tickHistogram)
 
 	// Setup loops
 	updater.loops = []*looper{

nonce/nonce.go

@@ -109,14 +109,17 @@ func NewNonceService(stats prometheus.Registerer, maxUsed int, prefix string) (*
 		Name: "nonces_generated",
 		Help: "A counter of nonces generated",
 	})
+	stats.MustRegister(noncesGenerated)
 	nonceValidations := prometheus.NewCounterVec(prometheus.CounterOpts{
 		Name: "nonces_validations",
 		Help: "A counter of nonce validations labelled by result",
 	}, []string{"result", "error"})
+	stats.MustRegister(nonceValidations)
 	nonceHeapLatency := prometheus.NewHistogram(prometheus.HistogramOpts{
 		Name: "nonce_heap_latency",
 		Help: "A histogram of latencies of heap pop operations",
 	})
+	stats.MustRegister(nonceHeapLatency)
 
 	return &NonceService{
 		earliest:         0,