Add Check of DB connections on healthcheck URL (#812)

lemur/common/health.py

@@ -7,10 +7,21 @@
 .. moduleauthor:: Kevin Glisson <kglisson@netflix.com>
 """
 from flask import Blueprint
+from lemur.database import db
 
 mod = Blueprint('healthCheck', __name__)
 
 
 @mod.route('/healthcheck')
 def health():
-    return 'ok'
+    try:
+        if healthcheck(db):
+            return 'ok'
+    except:
+        return 'db check failed'
+
+
+def healthcheck(db):
+    with db.engine.connect() as connection:
+        connection.execute('SELECT 1;')
+    return True