[libmultipath] fix empty map flushing
[libmultipath] fix empty map flushing

devmapper.c:dm_flush_map() should flush empty map, whatever the type the
caller asked it to limit to.

Noted by Maxim Kozover


grzn/multipath-tools-explained,vijaychauhan/multipath-tools,grzn/multipath-tools-explained,unakatsuo/multipath-tools,unakatsuo/multipath-tools,gebi/multipath-tools,vijaychauhan/multipath-tools,unakatsuo/multipath-tools