various: add %m in messages

Sometimes we want to suppress strerror() message because the are providing
something better. But in those cases, it seems it was just forgotten.

(cherry picked from commit 2e09b2235a27df3ada3542a2402b6e1727fc2c6c)
(cherry picked from commit b9f0194aabcce280121fb2f657e38e12f1f0a5b9)

src/core/bpf-lsm.c

@@ -84,7 +84,7 @@ static int prepare_restrict_fs_bpf(struct restrict_fs_bpf **ret_obj) {
         r = restrict_fs_bpf__load(obj);
         assert(r <= 0);
         if (r < 0)
-                return log_error_errno(r, "Failed to load BPF object");
+                return log_error_errno(r, "Failed to load BPF object: %m");
 
         *ret_obj = TAKE_PTR(obj);
 

src/userdb/userwork.c

@@ -556,7 +556,7 @@ static int run(int argc, char *argv[]) {
                                         return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Parent already died?");
 
                                 if (kill(parent, SIGUSR2) < 0)
-                                        return log_error_errno(errno, "Failed to kill our own parent.");
+                                        return log_error_errno(errno, "Failed to kill our own parent: %m");
                         }
                 }
 

src/volatile-root/volatile-root.c

@@ -127,7 +127,7 @@ static int run(int argc, char *argv[]) {
 
         r = query_volatile_mode(&m);
         if (r < 0)
-                return log_error_errno(r, "Failed to determine volatile mode from kernel command line.");
+                return log_error_errno(r, "Failed to determine volatile mode from kernel command line: %m");
         if (r == 0 && argc >= 2) {
                 /* The kernel command line always wins. However if nothing was set there, the argument passed here wins instead. */
                 m = volatile_mode_from_string(argv[1]);