Fix cleanspec for property_contexts

The CLs that split the property_contexts at
topic:prop_ctx_split status:merged broke incremental build,
which was later fixed in I22ecd1d3698404df352263fa99b56cb65247a23b.

The prop_ctx CLs were later reverted due to updater breakage as in
b/34370523. So, this change adds the property_contexts clean steps
to fix the incremental builds

Change-Id: Ic32b144dbfada3a6c34f9502099220e7e3c63682
Signed-off-by: Sandeep Patil <sspatil@google.com>

CleanSpec.mk

@@ -57,3 +57,6 @@ $(call add-clean-step, rm -rf $(PRODUCT_OUT)/root/nonplat_property_contexts)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/nonplat_property_contexts)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/root/plat_property_contexts)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/plat_property_contexts)
+
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/root/property_contexts)
+$(call add-clean-step, rm -rf $(PRODUCT_OUT)/recovery/root/property_contexts)