[dvsim/lint] Minor fixes for printout issues and result parser status

This adds a missing \n before the triple back-ticks around the tool
messages. Also, the position of the messages is corrected, and the
return value of the lint parser scripts is fixed.

Signed-off-by: Michael Schaffner <msf@google.com>
diff --git a/util/dvsim/LintCfg.py b/util/dvsim/LintCfg.py
index 13f9f2b..6683c62 100644
--- a/util/dvsim/LintCfg.py
+++ b/util/dvsim/LintCfg.py
@@ -184,10 +184,10 @@
                     break
 
             if has_msg:
-                results_str += "\n### Errors and Warnings for Build Mode `'" + mode.name + "'`\n"
+                fail_msgs += "\n### Errors and Warnings for Build Mode `'" + mode.name + "'`\n"
                 for hdr, key in hdr_key_pairs:
                     msgs = self.result.get(key)
-                    results_str += print_msg_list("#### " + hdr, msgs, self.max_msg_count)
+                    fail_msgs += print_msg_list("#### " + hdr, msgs, self.max_msg_count)
 
         if len(table) > 1:
             self.results_md = results_str + tabulate(