Use stressTestMultiplier in ByteBufferChannelTest timeout

Author: elizarov

core/kotlinx-coroutines-io/src/test/kotlin/kotlinx/coroutines/experimental/io/ByteBufferChannelTest.kt

@@ -29,7 +29,7 @@ import kotlin.test.fail
 
 class ByteBufferChannelTest : TestBase() {
     @get:Rule
-    val timeout = Timeout(100, TimeUnit.SECONDS)
+    val timeout = Timeout(100L * stressTestMultiplier, TimeUnit.SECONDS)
 
     @get:Rule
     private val failures = ErrorCollector()