Remove unused var DEFAULT_MAX_CACHE_SIZE
Remove unused var DEFAULT_MAX_CACHE_SIZE

In file: glance/image_cache/__init__.py, DEFAULT_MAX_CACHE_SIZE
is never used after declared, remove it and make glance code
tidy and pleasing.

Change-Id: I208f1dc63e2bc95bb6be94fdc88f9bfce069f67c

stevelle/glance,redhat-openstack/glance,saeki-masaki/glance,ozamiatin/glance,JioCloud/glance,citrix-openstack-build/glance,tanglei528/glance,openstack/glance,scripnichenko/glance,rajalokan/glance,paramite/glance,klmitch/glance,SUSE-Cloud/glance,vuntz/glance,wkoathp/glance,kfwang/Glance-OVA-OVF,darren-wang/gl,sigmavirus24/glance,openstack/glance,akash1808/glance,darren-wang/gl,wkoathp/glance,saeki-masaki/glance,ozamiatin/glance,akash1808/glance,citrix-openstack-build/glance,rickerc/glance_audit,rickerc/glance_audit,dims/glance,scripnichenko/glance,ntt-sic/glance,sigmavirus24/glance,klmitch/glance,paramite/glance,stevelle/glance,takeshineshiro/glance,cloudbau/glance,kfwang/Glance-OVA-OVF,cloudbau/glance,JioCloud/glance,tanglei528/glance,ntt-sic/glance,openstack/glance,SUSE-Cloud/glance,redhat-openstack/glance,dims/glance,vuntz/glance,rajalokan/glance,takeshineshiro/glance,jumpstarter-io/glance,jumpstarter-io/glance