[FIX] Fixed issues with duplicated subscription or missing on the list

[rafaelks]

@RocketChat/ios

Closes #2471
Closes #2403

[codecov]

Codecov Report

Merging #2493 into develop will decrease coverage by 0.1%.
The diff coverage is 73.52%.

@@             Coverage Diff             @@
##           develop    #2493      +/-   ##
===========================================
- Coverage    26.39%   26.29%   -0.11%     
===========================================
  Files          456      456              
  Lines        16929    16949      +20     
===========================================
- Hits          4469     4457      -12     
- Misses       12460    12492      +32

Impacted Files	Coverage Δ
...Chat/Models/Mapping/SubscriptionModelMapping.swift	87.5% <ø> (ø)	⬆️
...Controllers/Chat/ChatSections/MessageSection.swift	4.16% <ø> (ø)	⬆️
Rocket.Chat/Models/Message/UnmanagedMessage.swift	32.89% <ø> (ø)	⬆️
Rocket.Chat/API/Clients/MessagesClient.swift	58.17% <ø> (ø)	⬆️
...at/Views/Cells/Subscription/SubscriptionCell.swift	0% <0%> (ø)	⬆️
...ntrollers/Chat/MessagesViewControllerJoining.swift	70.45% <0%> (-1.64%)	⬇️
...odel/SubscriptionManager/SubscriptionManager.swift	0% <0%> (ø)	⬆️
...SubscriptionManager/SubscriptionManagerRooms.swift	26.66% <0%> (ø)	⬆️
Rocket.Chat/Models/Base/ModelHandler.swift	0% <0%> (ø)	⬆️
...Chat/Managers/Socket/Response/SocketHandlers.swift	57.5% <100%> (ø)	⬆️
... and 10 more

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[JoyWang1010]

It seems not ok....

[piepie314]

still exist some problems