Hob: Set empty DISTRO if "defaultsetup" is selected

In Hob advanced setting, if "defaultsetup" is selected, we need to
leave DISTRO variable not set in bitbake server.

Otherwise, defaultsetup.conf will be parsed twice, causing TMPDIR and
its related variables mess up.

(Bitbake rev: 863b14ebf2c7443ce6df362f24af6395e520edbc)

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/ui/crumbs/hobeventhandler.py

@@ -274,7 +274,8 @@ class HobHandler(gobject.GObject):
         self.server.runCommand(["setVariable", "IMAGE_FSTYPES", " ".join(image_fstypes).lstrip(" ")])
 
     def set_distro(self, distro):
-        self.server.runCommand(["setVariable", "DISTRO", distro])
+        if distro != "defaultsetup":
+            self.server.runCommand(["setVariable", "DISTRO", distro])
 
     def set_package_format(self, format):
         package_classes = ""