various: do not include file names directly in error messages

git grep -l 'Failed to open /'|xargs sed -r -i 's|"Failed to open (/[^ ]+): %m"|"Failed to open %s: %m", "\1"|g'
git grep -l $'Failed to open \'/'|xargs sed -r -i $'s|"Failed to open \'(/[^ ]+)\': %m"|"Failed to open %s: %m", "\\1"|g'
git grep -l "Failed to open /"|xargs sed -r -i $'s|"Failed to open (/[^ ]+), ignoring: %m"|"Failed to open %s, ignoring: %m", "\\1"|g'
+ some manual fixups.

src/userdb/userdbctl.c

@@ -1040,7 +1040,7 @@ static int display_services(int argc, char *argv[], void *userdata) {
                         return 0;
                 }
 
-                return log_error_errno(errno, "Failed to open /run/systemd/userdb/: %m");
+                return log_error_errno(errno, "Failed to open %s: %m", "/run/systemd/userdb/");
         }
 
         t = table_new("service", "listening");
@@ -1461,7 +1461,7 @@ static int load_credentials(int argc, char *argv[], void *userdata) {
                 /* xopen_flags= */ XO_LABEL,
                 /* mode= */ 0755);
         if (userdb_dir_fd < 0)
-                return log_error_errno(userdb_dir_fd, "Failed to open '/etc/userdb/': %m");
+                return log_error_errno(userdb_dir_fd, "Failed to open %s: %m", "/etc/userdb/");
 
         FOREACH_ARRAY(i, des->entries, des->n_entries) {
                 struct dirent *de = *i;