tree-wise: several cleanups for logging

- drop unnecessary SYNTHETIC_ERRNO() when the logger does not propagate
  error code,
- drop unnecessary '%m' in error message when the error code is
  specified with SYNTHETIC_ERRNO(),
- add missing full stop at the end of log message,
- use RET_GATHER(),
- add missing ", ignoring.",
- upeercase the first letter, etc., etc...

src/boot/bless-boot.c

@@ -388,7 +388,7 @@ static int verb_status(int argc, char *argv[], void *userdata) {
                 /* We didn't find any of the three? If so, let's try the next directory, before we give up. */
         }
 
-        return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Couldn't determine boot state: %m");
+        return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Couldn't determine boot state.");
 }
 
 static int verb_set(int argc, char *argv[], void *userdata) {
@@ -479,8 +479,7 @@ static int verb_set(int argc, char *argv[], void *userdata) {
                 return 0;
         }
 
-        log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Can't find boot counter source file for '%s': %m", target);
-        return 1;
+        return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Can't find boot counter source file for '%s'.", target);
 
 exists:
         log_debug("Operation already executed before, not doing anything.");

src/boot/bootctl-set-efivar.c

@@ -38,7 +38,7 @@ static int parse_timeout(const char *arg1, char16_t **ret_timeout, size_t *ret_t
                 (void) efi_loader_get_features(&loader_features);
                 if (!(loader_features & EFI_LOADER_FEATURE_MENU_DISABLE)) {
                         if (!arg_graceful)
-                                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Loader does not support 'menu-disabled': %m");
+                                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Loader does not support 'menu-disabled'.");
 
                         log_warning("Loader does not support 'menu-disabled', setting anyway.");
                 }

src/boot/bootctl-status.c

@@ -348,7 +348,7 @@ int verb_status(int argc, char *argv[], void *userdata) {
 
                 const char *path = arg_dollar_boot_path();
                 if (!path)
-                        return log_error_errno(SYNTHETIC_ERRNO(EACCES), "Failed to determine XBOOTLDR location: %m");
+                        return log_error_errno(SYNTHETIC_ERRNO(EACCES), "Failed to determine XBOOTLDR location.");
 
                 puts(path);
                 return 0;