Make init.userspace_reboot.is_supported a rw property

General recommendation is to avoid read-only properties, and instead control
"read-onlines" by only allowing init/vendor_init to set the property.

Since ro.init.userspace_reboot.is_supported was added in this release, and
nobody outside of the platform is querying it directly, it should be fine to
simply rename it.

Test: adb shell getprop init.userspace_reboot.is_supported
Test: atest CtsUserspaceRebootHostSideTestCases
Bug: 152803929
Change-Id: I7552d5ccc6e9b750a6081947eef8fcb027be13e1
Merged-In: I7552d5ccc6e9b750a6081947eef8fcb027be13e1
(cherry picked from commit 663cd35030d4d17625d896ef008b484b792619fe)
diff --git a/init/sysprop/InitProperties.sysprop b/init/sysprop/InitProperties.sysprop
index b876dc0..24c2434 100644
--- a/init/sysprop/InitProperties.sysprop
+++ b/init/sysprop/InitProperties.sysprop
@@ -31,6 +31,6 @@
     type: Boolean
     scope: Public
     access: Readonly
-    prop_name: "ro.init.userspace_reboot.is_supported"
+    prop_name: "init.userspace_reboot.is_supported"
     integer_as_bool: true
 }