minor: fix db names in tests with periods in description

Author: saghm

src/test/util/mod.rs

@@ -393,7 +393,10 @@ pub struct IsMasterCommandResponse {
 }
 
 pub fn get_default_name(description: &str) -> String {
-    let mut db_name = description.replace('$', "%").replace(' ', "_");
+    let mut db_name = description
+        .replace('$', "%")
+        .replace(' ', "_")
+        .replace('.', "_");
     // database names must have fewer than 64 characters
     db_name.truncate(63);
     db_name