Second chat session would not poll for events if application has been moved to background and then restored

[ALobastov]

Steps:

1. Start sample app
2. Log agent, keep Not Ready
3. Request chat session
4. While chat is in the queue, put app on background
5. Make agent Ready, accept chat, send some messages
6. Put mobile app on the foreground again - it shows all messages
7. End the chat session from mobile client (app is on the Help Me screen now)
8. Request another chat

Result: per xCode log, chat is successfully requested but the event polling does not start. Log shows:

[NetworkService.swift createRequest(method:url:headerFields:body:):26] curl -k -H "Expect:"
-X POST
-H "Content-Type: application/json; charset=utf-8"
-H "Authorization: MOBILE-API-140-327-PLAIN appId=1, clientId=38F89250-9EF4-498C-B248-42457D038B98"
-H "UserAgent: MobileClient"
-d '{"parameters":{"email":"mobilecustomer@example.com","caseNumber":"","last_name":"Customer","problem_description":"","first_name":"Mobile"},"from":"15550005555"}'
https://avl-mac-16.pl.bugfocus.com:443/clientweb/api/v2/chats?tenantUrl=example.com
[NetworkService.swift dataTask(using:with:):77] Received data: {"state":"ivr","ewt":"47","chat_id":"f1246f93-473f-48e3-9ee1-72845bc18612","is_new_chat":true}
[PollRequestService.swift pollAction():98] Skip poll request because another is in progress
Chat properties: ContactCenterChatSessionProperties(chatID: "f1246f93-473f-48e3-9ee1-72845bc18612", state: BPMobileMessaging.ContactCenterChatSessionState.ivr, estimatedWaitTime: Optional(47), isNewChat: true, phoneNumber: nil)

[ALobastov]

This is 100% reproducible when using actual physical device (iPhone XS Max, iOS 14.4); hard to reproduce with simulator.

[ALobastov]

Issue29.log.txt