FrameworksServicesTests: allow access to test.sys.boot.reason property

com.android.server.power.PowerManagerServiceTest#testGetLastShutdownReasonInternal due to "RuntimeException: failed to set system property"

W/roidJUnitRunner: type=1400 audit(0.0:6): avc: denied { write } for name="property_service" dev="tmpfs" ino=13178 scontext=u:r:platform_app:s0:c512,c768 tcontext=u:object_r:property_socket:s0 tclass=sock_file permissive=0
W/libc    : Unable to set property "test.sys.boot.reason" to "shutdown,thermal": connection failed; errno=13 (Permission denied)

Had to use precise property definition as com.android.phone accesses
test properties as well.

Test: compile
Bug: 78245377
Change-Id: I2cc810846f8615f2a2fae8e0d4f41de585b7abd7
diff --git a/private/property_contexts b/private/property_contexts
index 4433bdf..de09d4a 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -71,6 +71,7 @@
 persist.sys.boot.reason u:object_r:last_boot_reason_prop:s0
 sys.boot.reason         u:object_r:system_boot_reason_prop:s0
 pm.                     u:object_r:pm_prop:s0
+test.sys.boot.reason    u:object_r:test_boot_reason_prop:s0
 
 # Boolean property set by system server upon boot indicating
 # if device owner is provisioned.