core: Parse log environment settings again after applying manager environment

Currently, SYSTEMD_LOG_LEVEL set in the ManagerEnvironment property in system.conf
or user.conf doesn't affect the manager's logging level. Parsing the logging environment
variables again after pushing the manager environment into the process environment
block makes sure any new environment changes also get taken into account for logging.

src/core/main.c

@@ -2469,6 +2469,9 @@ static int parse_configuration(const struct rlimit *saved_rlimit_nofile,
         /* Push variables into the manager environment block */
         setenv_manager_environment();
 
+        /* Parse log environment variables again to take into account any new environment variables. */
+        log_parse_environment();
+
         return 0;
 }