Add SWF service URLs to default AWS config
Fix blkid call on RHEL 6

RHEL 6's version of util-linux lacks support for blkid's -d option.
This commit fixes euca-bundle-vol there by simply making it not use that
option.  It also raises an exception when that command fails.

Fixes TOOLS-520
Version bump (3.1.1)
Merge branch '3.1-maint'

Conflicts:
	euca2ools/__init__.py