Added am command to suppress config. changes during task resize.

This command is useful for testing during development, but at some
point we will decide if allowing configuration changes during resizing
is okay or merge in http://ag/759766 to suppress configuration changes
during resizing and deliver the new config. to the app.

This functionality will be reverted once we decide.

Bug: 24380097
Change-Id: I223c08bc939e564a78e70994b599770be9d4730d