Race condition when updating dashboard

[jkodumal]

Encountered with version 0.1.0-beta of the pod.

To reproduce, make changes on the LD dashboard and turn debugging on to poll rapidly.

2015-10-29 14:57:58.634 Converted[16401:2011110] *** Terminating app due to uncaught exception 'NSGenericException', reason: '*** Collection <__NSCFSet: 0x7fb9b1dc4140> was mutated while being enumerated.'
*** First throw call stack:
(
    0   CoreFoundation                      0x00000001073c5f45 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x0000000106e3fdeb objc_exception_throw + 48
    2   CoreFoundation                      0x00000001073c58a4 __NSFastEnumerationMutationHandler + 132
    3   CoreData                            0x0000000103d40704 -[NSManagedObjectContext executeFetchRequest:error:] + 2932
    4   Converted                           0x000000010345dc18 -[DataManager allEvents] + 328
    5   Converted                           0x000000010345de97 -[DataManager allEventsJsonData] + 119
    6   Converted                           0x000000010345af98 -[ClientManager syncWithServerForEvents] + 136
    7   Converted                           0x00000001034648db -[PollingManager eventPoll] + 187
    8   Converted                           0x00000001034647a6 __37-[PollingManager startEventPollTimer]_block_invoke + 38
    9   libdispatch.dylib                   0x000000010787549b _dispatch_client_callout + 8
    10  libdispatch.dylib                   0x00000001078688a5 _dispatch_source_latch_and_call + 1750
    11  libdispatch.dylib                   0x0000000107863830 _dispatch_source_invoke + 1057
    12  libdispatch.dylib                   0x000000010785da56 _dispatch_root_queue_drain + 1420
    13  libdispatch.dylib                   0x000000010785d4c5 _dispatch_worker_thread3 + 111
    14  libsystem_pthread.dylib             0x0000000107ba6a9d _pthread_wqthread + 729
    15  libsystem_pthread.dylib             0x0000000107ba43dd start_wqthread + 13
)
2015-10-29 14:57:58.637 Converted[16401:2010704] ClientManager processedConfig method called after receiving successful response from server
libc++abi.dylib: terminating with uncaught exception of type NSException

[gus-byrnesinnovation]

Fixed in https://github.com/launchdarkly/ios-client/pull/7/files.

Was related to:

http://stackoverflow.com/questions/9922145/what-is-nsmanagedobjectcontexts-performblock-used-for