test: return 0 if ignoring 'a' device health chars is requested

This allows lvconvert-raid-reshape-striped_to_linear.sh to succeed when
it reduces raid5 to two stripes before converting to raid1 and linear.

test/lib/check.sh

@@ -234,6 +234,7 @@ in_sync() {
 		[ $ignore_a -eq 0 ] && \
 			die "$lvm_name ($type$snap) in-sync, but 'a' characters in health status"
 		echo "$lvm_name ($type$snap) is not in-sync"
+		[ $ignore_a -eq 1 ] && return 0
 		return 1
 	fi