Use error_is_set() only when necessary

error_is_set(&var) is the same as var != NULL, but it takes
whole-program analysis to figure that out.  Unnecessarily hard for
optimizers, static checkers, and human readers.  Dumb it down to
obvious.

Gets rid of several dozen Coverity false positives.

Note that the obvious form is already used in many places.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/net/net.c b/net/net.c
index 2c3af20..41b3883 100644
--- a/net/net.c
+++ b/net/net.c
@@ -882,7 +882,7 @@
     qemu_opt_set(opts, "type", device);
 
     net_client_init(opts, 0, &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         qerror_report_err(local_err);
         error_free(local_err);
         monitor_printf(mon, "adding host network device %s failed\n", device);
@@ -918,17 +918,17 @@
     QemuOpts *opts;
 
     opts_list = qemu_find_opts_err("netdev", &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         goto exit_err;
     }
 
     opts = qemu_opts_from_qdict(opts_list, qdict, &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         goto exit_err;
     }
 
     netdev_add(opts, &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         qemu_opts_del(opts);
         goto exit_err;
     }
@@ -1152,7 +1152,7 @@
     Error *local_err = NULL;
 
     net_client_init(opts, 0, &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         qerror_report_err(local_err);
         error_free(local_err);
         return -1;
@@ -1167,7 +1167,7 @@
     int ret;
 
     ret = net_client_init(opts, 1, &local_err);
-    if (error_is_set(&local_err)) {
+    if (local_err) {
         qerror_report_err(local_err);
         error_free(local_err);
         return -1;