sd-device: make TAGS= property prefixed and suffixed with ":"

The commit 6f3ac0d517 drops the prefix and
suffix in TAGS= property. But there exists several rules that have like
`TAGS=="*:tag:*"`. So, the property must be always prefixed and suffixed
with ":".

Fixes #17930.

src/basic/set.h

@@ -151,4 +151,4 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(Set*, set_free_free);
 #define _cleanup_set_free_ _cleanup_(set_freep)
 #define _cleanup_set_free_free_ _cleanup_(set_free_freep)
 
-int set_strjoin(Set *s, const char *separator, char **ret);
+int set_strjoin(Set *s, const char *separator, bool wrap_with_separator, char **ret);