Fix wrong Exception messages

In two places we threw an IOException and the message was built using
JGitText.couldNotWriteFile. We specified 2 parameters, but this pattern
expects only one parameter. In both places we tried to rename a file,
that's why we wanted two parameters (src and target) for the exception
text.

I changed it to use JGitText.renameFileFailed which accepts two
parameters and fits better.

Change-Id: Ib8c2cf78f2b26ca2b97754fe91fdb20b30392415
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/api/StashDropCommand.java

@@ -219,7 +219,7 @@ public class StashDropCommand extends GitCommand<ObjectId> {
 				FileUtils.delete(stashFile);
 				if (!stashLockFile.renameTo(stashFile))
 					throw new JGitInternalException(MessageFormat.format(
-							JGitText.get().couldNotWriteFile,
+							JGitText.get().renameFileFailed,
 							stashLockFile.getPath(), stashFile.getPath()));
 			}
 		} catch (IOException e) {

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java

@@ -1154,7 +1154,7 @@ public class DirCacheCheckout {
 				FileUtils.rename(tmpFile, f);
 			} catch (IOException e) {
 				throw new IOException(MessageFormat.format(
-						JGitText.get().couldNotWriteFile, tmpFile.getPath(),
+						JGitText.get().renameFileFailed, tmpFile.getPath(),
 						f.getPath()));
 			}
 		}