Dell SC: Add check of current value on retype

Dell SC: Add check of current value on retype

The recently merged retype code for the Dell Storage
Center driver does not check if the new Storage Profile
value is different than the currently set value. While
this is mostly harmless since there isn't a lot of overhead
to setting the Storage Profile to its existing value, it
is still extra overhead and API calls that need to be
performed to complete the operation.

This adds a simple check to compare the current value against
the requested value to decide whether or not to perform the
retype operation. We only support retyping of the Storage
Profile, so if they are the same, just return true to
prevent a migration from happening.

Change-Id: I2d16b4129170cc8ecedfd3674b609badb27b9095