Fix Accept header and removed Content-Type from common headers
Fixes an issue where the number of retries was always set to 1.
Prefer Guava HttpHeaders over JAX-RS

jclouds code contains more instances of the former and Guava has
additional constants like CONTENT_MD5.
Update openstack-keystone RetryOnRenew to handle 408 errors with a BackoffLimitedRetryHandler
Make constants final classes instead of interfaces

This commit prohibits implementation of the empty interface and
instantiation of the class.  Refer to _Effective Java_ item 19 for
more background.
Migrate InputSupplier callers to ByteSource

A future version of Guava will remove InputSupplier.
Replace InputSupplierMap with Map<K, ByteSource>

A future version of Guava will remove InputSupplier.
Address CheckStyle violations
Replace deprecated calls to LoadingCache.apply
Updating EC2 test mocks to match changes in 79c289d
JCLOUDS-571 - Fix build to suppress maven parent.relativePath warnings at start of build
Fixed format and removed the trailing spaces
Override hashCode when equals overridden

Java 8 added a warning for this:

https://bugs.openjdk.java.net/browse/JDK-6563143
Add missing @Override annotations
JCLOUDS-573: Make sure to destroy all nodes created in the tests
Prefer ByteStreams over ByteArrayOutputStream
Prefer Guava Hashing over MessageDigest
Use ByteSource methods to create test input

Also avoids excessive system calls due to unbuffered writes.  Finally
migrate repeatingArrayByteSource to ByteSources.
Prefer File.delete over File.deleteOnExit

The former has deterministic behavior and avoids resource leaks.
[JCLOUDS-392] Remove dependency from Maps2. Make jclouds-core packages optionally imported from jclouds-scriptbuilder.