MFC r265318:

MFC r265318:
  For schemes that do an automatic partition aligning move this code to
  separate function.

MFC r265331:
  Prevent an unexpected shrinking on resizing due to alignment for MBR,
  PC98 and VTOC8 schemes.

MFC r265333:
  Add better error description for case when we are doing resize and
  scheme-specific method returns EBUSY.

MFC r265539:
  It is safe to allow shrinking, when aligned size is bigger than current.

git-svn-id: svn://svn.freebsd.org/base/stable/10@265910 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f