network: fix memory leak in networkBuildDhcpDaemonCommandLine()

hostsfilestr was not being freed. This will be turned into g_autofree
in an upcoming patch converting a lot more of the same file to using
g_auto*, but I wanted to make a separate patch for this first so the
other patch is simpler to review (and to make backporting easier).

The leak was introduced in commit 97a0aa2467

Signed-off-by: Laine Stump <laine@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/network/bridge_driver.c

@@ -1628,6 +1628,7 @@ networkBuildDhcpDaemonCommandLine(virNetworkDriverStatePtr driver,
     virObjectUnref(dnsmasq_caps);
     VIR_FREE(configfile);
     VIR_FREE(configstr);
+    VIR_FREE(hostsfilestr);
     VIR_FREE(leaseshelper_path);
     return ret;
 }