imsm: use timeout when waiting for reshape progress

imsm: use timeout when waiting for reshape progress

Waiting for reshape progress is done by using select() on sync_completed
to block until an exception condition is signalled on the
filedescriptor. This happens when the attribute's value is updated by
the kernel, but if the array is stopped when mdadm is blocked on
select() this will never happen, because this attribute is then removed
and apparently the kernel doesn't do sysfs_notify() when removing a
sysfs attribute. So set a 3 second timeout for the sysfs_wait() call.

Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NeilBrown <neilb@suse.com>