Fix logical partition grow overlaps extended partition end (#686668)

In certain situations with a mixture of partition alignments, the MiB
alignment option would try to set the end of a logical partition
beyond the end of the extended partition.  This, of course, is an
invalid partition geometry and the libparted library correctly reports
failure when this is attempted.

This enhancement to MiB alignment adds a check to see if the end of
the logical partition would be beyond the extended partition, and
adjusts the end of the logical partition if required.

Closes Bug #686668 - Growing logical partition overlaps end of
                     extended partition