IMSM: retry reading sync_completed during reshape

IMSM: retry reading sync_completed during reshape

The sync_completed after restarting a reshape
(for example - after reboot) is set to "delayed" until
mdmon changes the state. Mdadm does not wait for that change with
old kernels. If this condition occurs - it exits and reshape
is not continuing. This patch adds retry of reading sync_complete
with a delay. It gives time for mdmon to change the "delayed" state.

Signed-off-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>