Add ETag tests for IObjectStorageProvider.CreateObject

[sharwell]

The test suite for IObjectStorageProvider should include tests which set the ETag header during object uploads. This would include the following:

1. [ ] Verifying behavior when the ETag is correct.
2. [ ] Verifying behavior when the ETag does not match the uploaded data.
3. [ ] Verifying behavior when the ETag takes different forms; in particular, the quoted-string form described in the HTTP specification, and the unquoted-string form returned by some API calls.
4. [ ] Verifying behavior when the ETag is invalid, i.e. not the correct length or contains invalid characters.