polkit: Go back to using auth_admin_keep.

This was already used for active sessions, make it the same
for others.

ref: linuxmint/linuxmint/issues#629

data/org.nemo.root.policy.in

@@ -13,9 +13,9 @@
    <message gettext-domain="nemo">Files</message>
    <icon_name>gksu-root-terminal</icon_name>
    <defaults>
-     <allow_any>auth_admin</allow_any>
-     <allow_inactive>auth_admin</allow_inactive>
-     <allow_active>auth_admin</allow_active>
+     <allow_any>auth_admin_keep</allow_any>
+     <allow_inactive>auth_admin_keep</allow_inactive>
+     <allow_active>auth_admin_keep</allow_active>
    </defaults>
    <annotate key="org.freedesktop.policykit.exec.path">@bindir@/nemo</annotate>
    <annotate key="org.freedesktop.policykit.exec.allow_gui">true</annotate>