Don't use the whole free space when resizing partition to a larger size

Don't use the whole free space when resizing  partition to a larger size
on a disk with non zero stripesize (e.g. disks with 4k sector size)[1].
Also do not use automatic alignment when size is exactly specified, but
an alignment is not. Use automatic alignment only for case when user
omits both "-s" and "-a" options.

Reported by:	Mikael Fridh <frimik at gmail> [1]
Approved by:	re (kib)
MFC after:	1 week