D-Bus: User: Make AllGroups & AllPriv as const

AllGroups & AllPriv properties are designed to expose
the groups & privileges supported so that different customer
can mend the same to their needs. These 2 properties were
not marked as const, eventhough the it will act like one.
Calling the same explicitly now. These properties are read-only
const properties, which will not change it's value during
run-time.

Change-Id: I7f70980014f20e13cfec266534791eecbb345f24
Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
diff --git a/xyz/openbmc_project/User/Manager.interface.yaml b/xyz/openbmc_project/User/Manager.interface.yaml
index 3874071..5784ea1 100644
--- a/xyz/openbmc_project/User/Manager.interface.yaml
+++ b/xyz/openbmc_project/User/Manager.interface.yaml
@@ -101,11 +101,15 @@
 properties:
     - name: AllPrivileges
       type: array[string]
+      flags:
+          - const
       description: >
           Lists all available user privileges in the system.
 
     - name: AllGroups
       type: array[string]
+      flags:
+          - const
       description: >
           Lists all available groups in the system.