Add "| default" filter on AWS_GATHER_FACTS conditional in edx_service
Add "| default" filter on AWS_GATHER_FACTS conditional in edx_service

edx_service references AWS_GATHER_FACTS, which is a variable whose
default is set in the aws role. edx_service does not list a dependency
on aws in its meta/main.yml declaration, so it does not inherit
that default.

As a result, operators writing their own playbook (which may not include
the aws role) would have to set AWS_GATHER_FACTS: false, just to use
any service that depends on edx_service.

openedx_native.yml does set AWS_GATHER_FACTS: false, so its users are
not affected by this problem, but relying on that is really a kludge:
the edx_service role should be able to function on its own (plus its
declared dependencies), not rely on setting a variable whose default
lives in another role that it does not depend on.

Add a "| default(false)" filter to the AWS_GATHER_FACTS conditional,
so that operators not using AWS at all (and hence not enabling the aws
role) are able to use the edx_service role without having to set that
variable.

mitodl/configuration,edx/configuration,arbrandes/edx-configuration,stvstnfrd/configuration,mitodl/configuration,EDUlib/configuration,EDUlib/configuration,arbrandes/edx-configuration,arbrandes/edx-configuration,stvstnfrd/configuration,EDUlib/configuration,EDUlib/configuration,edx/configuration,stvstnfrd/configuration,mitodl/configuration,edx/configuration,stvstnfrd/configuration,stvstnfrd/configuration,arbrandes/edx-configuration,edx/configuration,EDUlib/configuration,mitodl/configuration,arbrandes/edx-configuration