nwfilter: use g_strdup instead of VIR_STRDUP

Replace all occurrences of
  if (VIR_STRDUP(a, b) < 0)
     /* effectively dead code */
with:
  a = g_strdup(b);
Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/nwfilter/nwfilter_dhcpsnoop.c

@@ -1093,8 +1093,7 @@ virNWFilterSnoopDHCPOpen(const char *ifname, virMacAddr *mac,
          * generate much more traffic than if we filtered by VM and
          * braodcast MAC as well
          */
-        if (VIR_STRDUP(ext_filter, filter) < 0)
-            return NULL;
+        ext_filter = g_strdup(filter);
     }
 
     handle = pcap_create(ifname, pcap_errbuf);

src/nwfilter/nwfilter_driver.c

@@ -205,8 +205,7 @@ nwfilterStateInitialize(bool privileged,
 
     nwfilterDriverLock();
 
-    if (VIR_STRDUP(driver->stateDir, RUNSTATEDIR "/libvirt/nwfilter") < 0)
-        goto error;
+    driver->stateDir = g_strdup(RUNSTATEDIR "/libvirt/nwfilter");
 
     if (virFileMakePathWithMode(driver->stateDir, S_IRWXU) < 0) {
         virReportSystemError(errno, _("cannot create state directory '%s'"),
@@ -252,8 +251,7 @@ nwfilterStateInitialize(bool privileged,
         goto error;
     }
 
-    if (VIR_STRDUP(driver->configDir, SYSCONFDIR "/libvirt/nwfilter") < 0)
-        goto error;
+    driver->configDir = g_strdup(SYSCONFDIR "/libvirt/nwfilter");
 
     if (virFileMakePathWithMode(driver->configDir, S_IRWXU) < 0) {
         virReportSystemError(errno, _("cannot create config directory '%s'"),
@@ -261,8 +259,7 @@ nwfilterStateInitialize(bool privileged,
         goto error;
     }
 
-    if (VIR_STRDUP(driver->bindingDir, RUNSTATEDIR "/libvirt/nwfilter-binding") < 0)
-        goto error;
+    driver->bindingDir = g_strdup(RUNSTATEDIR "/libvirt/nwfilter-binding");
 
     if (virFileMakePathWithMode(driver->bindingDir, S_IRWXU) < 0) {
         virReportSystemError(errno, _("cannot create config directory '%s'"),