scaleio driver invalid format string

[Eric Harney]

Seen when running unit tests.

Captured stderr:
~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "/usr/lib64/python2.7/logging/__init__.py", line 859, in emit
        msg = self.format(record)
      File "/usr/lib64/python2.7/logging/__init__.py", line 732, in format
        return fmt.format(record)
      File "/usr/lib64/python2.7/logging/__init__.py", line 471, in format
        record.message = record.getMessage()
      File "/usr/lib64/python2.7/logging/__init__.py", line 335, in getMessage
        msg = msg % self.args
    ValueError: incomplete format
    Logged from file scaleio.py, line 573