The empty metadata service can be used to run plugins that do not
rely on metadata service information, like setting NTP, MTU,
extending volumes, local scripts execution, licensing, etc.
It can be used also as a fallback metadata service, in case no other
previous metadata service could be loaded.
EmptyMetadataService does not support the following plugins:
* cloudbaseinit.plugins.windows.createuser.CreateUserPlugin
* cloudbaseinit.plugins.common.setuserpassword.SetUserPasswordPlugin
* cloudbaseinit.plugins.common.sshpublickeys.SetUserSSHPublicKeysPlugin
* cloudbaseinit.plugins.windows.winrmcertificateauth.ConfigWinRMCertificateAuthPlugin
If any of the plugins defined above are executed,
they will fail with exception NotExistingMetadataException. The reason
for the hardcoded failure is that these plugins rely on metadata to execute
correctly. If metadata like username or password is not provided,
these plugins can lock or misconfigure the user, leading to unwanted problems.
Implements: blueprint empty-metadata-provider
Change-Id: I5fb88a07bf72321d0f66b16d151bf6059b448580
b5e3c42f39