If tryLock fails to get the lock another gc has it

Change-Id: Ifd3bbcc5e0591883b774d23256949a83010ea134
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
index 7feb506..f25feee 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
@@ -1650,7 +1650,7 @@ boolean lock() throws IOException {
 				channel = f.getChannel();
 				lock = channel.tryLock();
 				if (lock == null || !lock.isValid()) {
-					failedToLock();
+					gcAlreadyRunning();
 					return false;
 				}
 				channel.write(ByteBuffer