libcore: removed unnecessary code in SSLSocketTest

Was possibly causing a race condition (see b/21776011),
for instance, in case readFirstReceivedChunkFuture
was still executing IoUtils#closeQuietly while the
thread was cancelled.

Bug: 21776011
(cherry picked from commit c22dd77f727262ed8105b8b638aeb817997914fd)

Change-Id: Ibb20a98102d5bdc9ac3eaa0b875801ab218356f1
diff --git a/luni/src/test/java/libcore/javax/net/ssl/SSLSocketTest.java b/luni/src/test/java/libcore/javax/net/ssl/SSLSocketTest.java
index 7e05054..bf2d0f8 100644
--- a/luni/src/test/java/libcore/javax/net/ssl/SSLSocketTest.java
+++ b/luni/src/test/java/libcore/javax/net/ssl/SSLSocketTest.java
@@ -1709,13 +1709,6 @@
                         return null;
                     } finally {
                         IoUtils.closeQuietly(client);
-
-                        // Cancel the reading task. If this task succeeded, then the reading task
-                        // is done and this will have no effect. If this task failed prematurely,
-                        // then the reading task might get unblocked (we're interrupting the thread
-                        // it's running on), will fail early, and we'll thus save some time in this
-                        // test.
-                        readFirstReceivedChunkFuture.cancel(true);
                     }
                 }
             });