Only check run loop mode if currentRunLoop == self.runLoop
Only check run loop mode if currentRunLoop == self.runLoop

This ensures that if .waitUntilExit() is a different run loop than
.run() was called on, .waitUntilExit() won't return before
self.isRunning becomes false.

apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation