tree-wide: when %m is used in log_*, always specify errno explicitly

All those uses were correct, but I think it's better to be explicit.
Using implicit errno is too error prone, and with this change we can require
(in the sense of a style guideline) that the code is always specified.

Helpful query: git grep -n -P 'log_[^s][a-z]+\(.*%m'

src/shared/install.c

@@ -3045,7 +3045,7 @@ int unit_file_get_list(
                         if (errno == ENOENT)
                                 continue;
                         if (IN_SET(errno, ENOTDIR, EACCES)) {
-                                log_debug("Failed to open \"%s\": %m", *i);
+                                log_debug_errno(errno, "Failed to open \"%s\": %m", *i);
                                 continue;
                         }