Remove usage of IOException(Throwable) not available on Java 5

Change-Id: I386aa77fb78bed3fb38a3ce46eaeb47df95fdde3
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/transport/HttpAuthMethod.java

@@ -517,7 +517,9 @@ abstract class HttpAuthMethod {
 				conn.setRequestProperty(HDR_AUTHORIZATION, getType().name()
 						+ " " + Base64.encodeBytes(token)); //$NON-NLS-1$
 			} catch (GSSException e) {
-				throw new IOException(e);
+				IOException ioe = new IOException();
+				ioe.initCause(e);
+				throw ioe;
 			}
 		}
 	}