When logging out of a web session while offline, logging back in results in failure to get a new session token - the old token (which is expired) is still stored in the cookie header.

Steps to reproduce:
1) Open the latest attached project.
2) Build for iOS.
3) Run on a device (make sure it's connected to the Internet).
- Observe the Xcode console.

Three web requests are made - first request, which is used to log in normally, second request, which is made after logging out while being offline and third request, which is made after clearing the cookie header. The second request returns "Already logged in", because the expired session token is still in the cookie header. This does not occur on the Editor. Tested with Mono2x and IL2CPP.

Reproduced on:
5.6.0a5, 5.5.0f3, 5.4.3p1, 5.3.7p1

Devices tested:
iPad Mini iOS 9.3.5
iPhone 7 iOS 10.2