get_loop_name should return an empty name if it isn't found (#980510)
get_loop_name should return an empty name if it isn't found (#980510)

Callers expect a name or "" not an error.

Related: rhbz#980510

jkonecny12/blivet,AdamWill/blivet,vpodzime/blivet,dwlehman/blivet,rvykydal/blivet,vojtechtrefny/blivet,rvykydal/blivet,AdamWill/blivet,dwlehman/blivet,vpodzime/blivet,rhinstaller/blivet,rhinstaller/blivet,vojtechtrefny/blivet,jkonecny12/blivet