added disable_vabc field to install_plan

Test: tested compilation. Applied OTA to cuttlefish instance with VABC
flag disabled.

Change-Id: I2d5756a58deb3d4bf7e80983294746c91aebeccb
diff --git a/common/constants.h b/common/constants.h
index b862549..f27d2db 100644
--- a/common/constants.h
+++ b/common/constants.h
@@ -176,6 +176,8 @@
 // Proxy URL to use for downloading OTA. This will be forwarded to libcurl
 static constexpr const auto& kPayloadPropertyNetworkProxy = "NETWORK_PROXY";
 
+static constexpr const auto& kPayloadDisableVABC = "DISABLE_VABC";
+
 // Set "SWITCH_SLOT_ON_REBOOT=0" to skip marking the updated partitions active.
 // The default is 1 (always switch slot if update succeeded).
 static constexpr const auto& kPayloadPropertySwitchSlotOnReboot =