Confusing and incorrect data units in HarddriveStorage and SanStorage getMaxTransferRate()

[manoelcampos]

Actual behavior

The HarddriveStorage.getMaxTransferRate() defines the disk transfer rate in Megabytes/sec.
The SanStorage overrides such a method by returning the minimum value
between themaxDataRate and the bandwidth. However, the last one is defined in Mbits/sec instead of Megabytes/sec. That makes the method return data in different units depending on if maxDataRate is lower than the bandwidth or not.

Megabytes/sec is the usual unit for disk transfer rate. However, since SanStorage extends HarddriveStorage, it's also confusing to have different units for the same method.

Expected behavior

maxDataRate and the bandwidth should be defined in Megabits/sec.
The default maxTransferRate for HarddriveStorage must also be converted to Megabits/sec.

If the issue is related to a specific method, provide a test case that fails in order to show the problem

New unit tests were added to both classes.