Fix up the db.get_last_modified_time() output

Explicitly return just the data, not a list.

Change-Id: Ia4344faba039c771b5aad2c6e3aed516d2ef96ec
diff --git a/db/db.py b/db/db.py
index 180a934..21ead71 100644
--- a/db/db.py
+++ b/db/db.py
@@ -552,7 +552,7 @@
     def get_last_modified_time(self):
         sql = "SELECT last_modified FROM state"
         self.cursor.execute(sql)
-        return self.cursor.fetchone()
+        return self.cursor.fetchone()[0]
 
     # Grab one row of a query on one column; useful as a quick wrapper
     def _get_row(self, table, field, value):