Adding tests to Create forced operation with different contexts.

Verify that the clients (for ex: clients with `vold` context) with
`req_forced_op` permission are allowed to create forced (unpruneable)
operations otherwise the creation of forced operation is denied.

Bug: 194359114
Test: atest keystore2_client_test
Change-Id: I73d85ac127274e623095e233368b0211f6738d6e
diff --git a/keystore2/test_utils/key_generations.rs b/keystore2/test_utils/key_generations.rs
index f8628ee..6398f31 100644
--- a/keystore2/test_utils/key_generations.rs
+++ b/keystore2/test_utils/key_generations.rs
@@ -30,6 +30,8 @@
 
 /// Shell namespace.
 pub const SELINUX_SHELL_NAMESPACE: i64 = 1;
+/// Vold namespace.
+pub const SELINUX_VOLD_NAMESPACE: i64 = 100;
 
 /// SU context.
 pub const TARGET_SU_CTX: &str = "u:r:su:s0";