Grow: When setting component size make sure components are ready.

Grow: When setting component size make sure components are ready.

If you change the size of a member of an array (e.g. it might be a
dm device that can be resized, or on a smart storage device), md
doesn't notice and so the space cannot be used without explicitly
telling md that the device is bigger.

This change causes "mdadm --grow --size=...." to make sure each
component device is making at least that much space available if it
can.

Normally usage of "--size=max" will cause all devices to make max
space available, the md will use as much as it can of that.

Signed-off-by: NeilBrown <neilb@suse.de>