This commit introduces BEHAVE_FLAGS as a new parameter in concourse.
This will help us run specific tests within a specific scenario, it used
to be just all or nothing. Now we can separate multi-host testing vs
single host testing.

Add tests for gppkg --clean for multi-host
 * gppkg --clean should install to the segment host with no gppkg
 * gppkg --clean should remove on all segment hosts when gppkg does not exist in master