Add label for persist.pm.mock-upgrade

This property is used for testing purposes when verifying the
behavior when an OTA occurs. It should be readable by the
system server, and be settable by the shell.

Test: Set property from shell, read with PackageManager
Bug: 140992644
Change-Id: I39ad9b7961208f02fa45011215c2ff5ac03b7380
diff --git a/private/property_contexts b/private/property_contexts
index 55445ec..b77a944 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -59,6 +59,7 @@
 persist.log.tag         u:object_r:log_tag_prop:s0
 persist.mmc.            u:object_r:mmc_prop:s0
 persist.netd.stable_secret      u:object_r:netd_stable_secret_prop:s0
+persist.pm.mock-upgrade u:object_r:mock_ota_prop:s0
 persist.sys.            u:object_r:system_prop:s0
 persist.sys.safemode    u:object_r:safemode_prop:s0
 persist.sys.theme       u:object_r:theme_prop:s0