Adds granularity support in OpenStack vim config

Adds global config class in core
Reorders common_consumer conditional blocks
Adds support for OS_DEFAULT_GRANULARITY env var
Modifies tests to support changes

Change-Id: I873b8d24814825bff6e628092942bf16fa5e2a03
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>