JCLOUDS-225: Setting 'clean install' as default release preparation goals

Partially reverts 8cc82b0. Thanks to @iocanel for hunting that down!
Upgrade jclouds-karaf to Guava 15.0-rc1
Upgrade to Guava 15.0

Release notes:

https://code.google.com/p/guava-libraries/wiki/Release15
Allow stdin for blobstore writes

Note that we must spool input to disk via FileBackedOutputStream when
stream size exceeds some threshold to avoid exhausting memory.  We
cannot generally use streaming writes since some providers like AWS-S3
do not support chunked encoding:

http://aws.amazon.com/articles/1109?_encoding=UTF8&jiveRedirect=1#14