Tighten up format_* methods for DM names
Tighten up format_* methods for DM names

Format the string only once and fix up the indices in the expect()
calls according to the fact that uuids get to be one character longer than
names.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

stratis-storage/stratisd,mulkieran/stratisd,stratis-storage/stratisd,trgill/stratisd,stratis-storage/stratisd,mulkieran/stratisd,trgill/stratisd