Use 'primary' for MSN terminology instead of 'leader'

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

src/occupant.rs

@@ -91,7 +91,7 @@ impl Occupant {
         for (i, session) in self.sessions.iter().enumerate() {
             if &own_session == session {
                 if i == 0 {
-                    // Leader session
+                    // Primary session
                     self.sessions[0] = own_session;
                     return Ok(());
                 }