s4-provision Use ProvisioningError and the eadb

s4-provision Use ProvisioningError and the eadb

The eadb flag tells us to avoid using system extended attributes, typcially if we
are not running as root (ie, in a test environment).

The ProvisioningError class allows us to return failures to the upgrade_from_s3 script
which can then be detected correctly by the selftest framework.

Andrew Bartlett