Crash after the failure of iAP data session creation

[t-yoshii]

Bug Report

Crash happens after the failure of iAP data session creation due to assertion check failure.

Even createSession in SDLIAPDataSession#startSession failed including retry (3 times), [self.ioStreamThread start];is called, this causes assertion failure at https://github.com/smartdevicelink/sdl_ios/blob/develop/SmartDeviceLink/SDLIAPDataSession.m#L322

Jun 21 18:03:37 iPhoneXS-M00326 CTSLang(ExternalAccessory)[323] <Notice>: ERROR - opening session failed
 :
Jun 21 18:03:37 iPhoneXS-M00326 CTSLang(SmartDeviceLink)[323] <Notice>: 18:03:37:448 \M-b\M^Z\M-* VERBOSE com.sdl.lifecycle (SDL)Transport:SDLIAPTransport:-[SDLIAPTransport dataSessionShouldRetry]:415 - Retrying the data session
 :
// Failed 3 times
Jun 21 18:03:37 iPhoneXS-M00326 CTSLang(SmartDeviceLink)[323] <Notice>: 18:03:37:448 \M-p\M^_\M^T\M-6 WARNING com.sdl.lifecycle (SDL)Transport:SDLIAPTransport:-[SDLIAPTransport sdl_establishSessionWithAccessory:]:356 - Surpassed allowed retry attempts (3), dismissing setup

Jun 21 18:03:37 iPhoneXS-M00326 CTSLang(Foundation)[323] <Notice>: *** Assertion failure in -[SDLIAPDataSession sdl_accessoryEventLoop], ...../SmartDeviceLink/SDLIAPDataSession.m:325

Jun 21 18:03:37 iPhoneXS-M00326 CTSLang(CoreFoundation)[323] <Notice>: *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Session must be assigned before calling'
*** First throw call stack:
(0x200f223a8 0x200127d00 0x200e37780 0x20191232c 0x1050929a4 0x20188ac4c 0x2019c0e54 0x200b2a908 0x200b2a864 0x200b32dcc)
Jun 21 18:03:37 iPhoneXS-M00326 CTSScreensApp_ms(Foundation)[325] <Notice>: *** Assertion failure in -[SDLIAPDataSession sdl_accessoryEventLoop], ...../SmartDeviceLink/SDLIAPDataSession.m:325

Reproduction Steps

1. EA data session creation failed for some reason.

Expected Behavior

2. SDLIAPTransport just stops retrying the session creation.

Observed Behavior

2. App crashes

OS & Version Information

iOS Version: iOS11, 12
SDL iOS Version: develop branch daa57de (6.2.3 +)
Testing Against: Our internal devboard/OEM HU

Test Case, Sample Code, and / or Example App

I will create PR