Ensures NetApp iSCSI driver correctly compares int values for size

The NetApp iSCSI driver needs to verify that the new size requested
during an extend operation does not exceed the max_resize of the
lun.  However, the driver was doing a >= compare against str values
of the sizes rather than the int values.  This caused the incorrect
code path to be used in certain situations.

Change-Id: I8bc66c71db6b469c7adf00ce8b5091513fccb740
Closes-Bug: 1281279
(cherry picked from commit a1d78df1b7c95dbb5024023662932cd94313dd58)