qemu: properly handle '=' in the VNC socket path

If a domain name contains a '=' and the unix socket path is
auto-generated or socket path provided by user contains '=' QEMU
is unable to properly parse the command line.  In order to make it
work we need to use the new command line syntax for VNC if it's
available, otherwise we can use the old syntax.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1352529Signed-off-by: NPavel Hrdina <phrdina@redhat.com>

src/qemu/qemu_command.c

@@ -7784,7 +7784,10 @@ qemuBuildGraphicsVNCCommandLine(virQEMUDriverConfigPtr cfg,
 
     switch (glisten->type) {
     case VIR_DOMAIN_GRAPHICS_LISTEN_TYPE_SOCKET:
-        virBufferAddLit(&opt, "unix:");
+        if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_VNC_MULTI_SERVERS))
+            virBufferAddLit(&opt, "vnc=unix:");
+        else
+            virBufferAddLit(&opt, "unix:");
         virQEMUBuildBufferEscapeComma(&opt, glisten->socket);
         break;