Disallow resizing of LVM2 PVs which are members of exported VGs (#670171)

When an inactive LVM2 Volume Group is exported it makes it unknown to
the local system, ready for moving the member Physical Volumes to
another system, where the VG can be imported and used.  In this state a
PV can't be resized.

    # lvm pvresize /dev/sda10
      Volume group Test-VG1 is exported
      Unable to read volume group "Test-VG1".
      0 physical volume(s) resized / 1 physical volume(s) not resized
    # echo $?
    5

Fix this by preventing resizing of such a PV.  This has been coded in a
generic way using new function filesystem_resize_disallowed() to
determine whether a file system is allowed to be resized or not.  For
a file system which can be resized, but is currently not allowed to be
resized, the behaviour is as follows:

1)  Pasting into unallocated space is limited to creating a new
    partition which is the same size as the copied partition.

2)  Resizing the partition is disallowed, only moving the partition is
    allowed.

3)  Pasting into an existing partition will only copy the file system.
    If the destination partition is larger a warning will report that
    growing the file system is not currently allowed.

4)  Checking a partition will also report a warning that growing the
    file system is not currently allowed.

This is exactly the same behaviour as for a file system which does not
implement resizing, except for a different warning message.

Bug #670171 - Add LVM PV read-write support