StreamCopyThread: flush cannot interrupt a write

Because flush calls interrupt with writeLock held, it cannot interrupt
a write.  Simplify by no longer defending against that.

Change-Id: Ib0b39b425335ff7b0ea1b1733562da5392576a15

org.eclipse.jgit/src/org/eclipse/jgit/util/io/StreamCopyThread.java

@@ -146,19 +146,9 @@ public class StreamCopyThread extends Thread {
 
 					synchronized (writeLock) {
 						boolean writeInterrupted = Thread.interrupted();
-						for (;;) {
+						dst.write(buf, 0, n);
-							try {
+						if (writeInterrupted) {
-								dst.write(buf, 0, n);
+							interrupt();
-							} catch (InterruptedIOException wakey) {
-								writeInterrupted = true;
-								continue;
-							}
-
-							// set interrupt status, which will be checked
-							// when we block in src.read
-							if (writeInterrupted)
-								interrupt();
-							break;
 						}
 					}
 				} catch (IOException e) {