Merge pull request #1183 from aplowe/1.5.x

openstack-nova: NPE in SecurityGroupApi.delete()
Work around failed metadata lookups with Rackspace

Previously BlobStore.list and thus BlobStore.clearContainer serialized
on synchronous and failed CDN lookups.  This effectively prevents
clearing any large container.  We cache a negative entry to work
around this.  This commit is similar to commit 3c7b965 to
hpcloud-objectstorage.
Merge pull request #1195 from maginatics/rax-list-container-1.5.x

Work around failed metadata lookups with Rackspace
Call BlobUtils.clearContainer directly

BaseAsyncBlobStore.clearContainer returns a Future which we previously
did not manage correctly, hanging when deleting non-existent
containers.  Call BlobUtils.clearContainer directly to address this.
Merge pull request #1239 from maginatics/delete-container-hang-1.5.x

Call BlobUtils.clearContainer directly
support changing credentials at runtime
accomodate runtime credential changes
ensure identity/credential properties are not needed when using credential supplier
added AWS temporary security credentials and integrated with FormSigner
integrated s3 request signing with temporary credentials
fixed bug in STS query signing
added STS api for temporary credentials
promoted aws-sts to top-level
issue #1165: add read-only zone api for route53
first functionality in dynect: session api
issue #1165: added skeleton for UltraDNS WS provider
changed ultradns to use https and added error handling
added zone list and get commands to ultradns
true-up security section for UltraDNS
added Task api for UltraDNS