[BUG] [iOS] Calling SDK 2.1.0-beta.1 - Re-joining a teams meeting shows displayName as "External"

**Describe the bug**

Re-joining teams meeting after getting removed by teams client user, occasionally produces an empty displayName. The displayName only shows "External", instead of "UserName (External)"

**To Reproduce**
Steps to reproduce the behavior:
1. Join team's meeting from iOS Composite demo app with a display name
2. Kick yourself out of meeting using the "Remove from meeting" (i.e. using a Teams client user)
3. It takes you back to the home screen which has the same details (i.e. token, display name, meeting link)
4. Rejoin meeting with same details (without toggling camera/ mic)
5. In the Participants list on Teams it only displays "(External)"

**Expected behavior**
When you join a teams meeting, it should display "UserName (External)"

**Screenshots**

**Setup (please complete the following information):**
- OS: [e.g. iOS]
- IDE : [e.g. IntelliJ]
- Version of the Library used

**Additional context**
- After joined teams meeting, turning on your camera corrects the display name (i.e. "Name (External)")
- Toggling the mute button also produces the correct display name
- Joining the call with both camera on & mic unmuted produces the expected display name (This step doesn't seem to be constant, on some occasions the display name still appeared as "(External)")

**Information Checklist**
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