Fix assignment of comparison against zero

Assign the value we're comparing:
(val = func()) < 0
instead of assigning the comparison value:
(val = func() < 0)

Both were introduced along with the code,
the TLS tests by commit bd789df in 0.9.4
net events by commit de87691 in 1.2.2.

Note that the event id type fix is a no-op:
vshNetworkEventIdTypeFromString can only return
-1 (failure) and the event is never used or
0 (the only possible event) and the value of 0 < 0 is still 0.

tests/virnettlshelpers.c

@@ -383,7 +383,7 @@ testTLSGenerateCert(struct testTLSCertReq *req,
      * If no 'ca' is set then we are self signing
      * the cert. This is done for the root CA certs
      */
-    if ((err = gnutls_x509_crt_sign(crt, ca ? ca : crt, privkey) < 0)) {
+    if ((err = gnutls_x509_crt_sign(crt, ca ? ca : crt, privkey)) < 0) {
         VIR_WARN("Failed to sign certificate %s", gnutls_strerror(err));
         abort();
     }
@@ -391,7 +391,7 @@ testTLSGenerateCert(struct testTLSCertReq *req,
     /*
      * Finally write the new cert out to disk
      */
-    if ((err = gnutls_x509_crt_export(crt, GNUTLS_X509_FMT_PEM, buffer, &size) < 0)) {
+    if ((err = gnutls_x509_crt_export(crt, GNUTLS_X509_FMT_PEM, buffer, &size)) < 0) {
         VIR_WARN("Failed to export certificate %s", gnutls_strerror(err));
         abort();
     }

tools/virsh-network.c

@@ -1238,7 +1238,7 @@ cmdNetworkEvent(vshControl *ctl, const vshCmd *cmd)
         vshError(ctl, "%s", _("either --list or event type is required"));
         return false;
     }
-    if ((event = vshNetworkEventIdTypeFromString(eventName) < 0)) {
+    if ((event = vshNetworkEventIdTypeFromString(eventName)) < 0) {
         vshError(ctl, _("unknown event type %s"), eventName);
         return false;
     }