rootfs.py: change the logic in _uninstall_unneeded

Previously, if we have 'package-management' and 'read-only-rootfs'
both in IMAGE_FEATRUES, we would meet the following error at system
start-up.

	rm: can't remove '/etc/rcS.d/S99run-postinsts': Read-only file system

However, what's really expected is that when there's no postinstall
script at system start-up, the /etc/rcS.d/S99run-postinsts should not
even be there.

Whether or not to remove the init script symlinks to run-postinsts should
not depend on whether we have 'package-management' in IMAGE_FEATURES; rather,
it should only depend on whether we have any postinstall script left to run
at system start-up.

This patch changes the _uninstall_unneeded function based on the logic
stated above.

[YOCTO #6257]

(From OE-Core rev: d51b1ced88958d31a1596e37db871257fe013446)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/rootfs.py

@@ -130,11 +130,19 @@ class Rootfs(object):
         self._cleanup()
 
     def _uninstall_uneeded(self):
+        # Remove unneeded init script symlinks
+        delayed_postinsts = self._get_delayed_postinsts()
+        if delayed_postinsts is None:
+            if os.path.exists(self.d.expand("${IMAGE_ROOTFS}${sysconfdir}/init.d/run-postinsts")):
+                self._exec_shell_cmd(["update-rc.d", "-f", "-r",
+                                      self.d.getVar('IMAGE_ROOTFS', True),
+                                      "run-postinsts", "remove"])
+
+        # Remove unneeded package-management related components
         if base_contains("IMAGE_FEATURES", "package-management",
                          True, False, self.d):
             return
 
-        delayed_postinsts = self._get_delayed_postinsts()
         if delayed_postinsts is None:
             installed_pkgs_dir = self.d.expand('${WORKDIR}/installed_pkgs.txt')
             pkgs_to_remove = list()
@@ -154,10 +162,6 @@ class Rootfs(object):
                 # Update installed_pkgs.txt
                 open(installed_pkgs_dir, "w+").write('\n'.join(pkgs_installed))
 
-            if os.path.exists(self.d.expand("${IMAGE_ROOTFS}${sysconfdir}/init.d/run-postinsts")):
-                self._exec_shell_cmd(["update-rc.d", "-f", "-r",
-                                      self.d.getVar('IMAGE_ROOTFS', True),
-                                      "run-postinsts", "remove"])
         else:
             self._save_postinsts()