[INTERNAL] m.VariantManagement: check if manage view dialog still exists after manage cancel event
[INTERNAL] m.VariantManagement: check if manage view dialog still exists
after manage cancel event

Change-Id: I4b58ad9cbab9edf76bbc5bc331b16299dc3f20fa

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5