[Bug]: CopyFileTask does not close streams on exception

### Issue

`CopyFileTask` does not close its input and output streams when there is an exception while writing.

### Repro Steps

1. Use `CopyFile` to copy a file from an external USB drive to a location on the android device. Use a large file so the copy takes a while.
2. Remove the USB drive during copy.
3. Application crashes.

### Investigation

When the IO Exception occurs, Android kills any processes that still have open handles on files on the USB drive. As evidence, check that logcat shows `D/voldUtils: KillProcessesUsingPath: path=/mnt/media_rw/XXXX-XXXX: Success` around the time of the IO exception.

### Suggested Fix

Move `in.close()` and `out.close()` into a `finally` block in [this function](https://github.com/itinance/react-native-fs/blob/master/android/src/main/java/com/rnfs/RNFSManager.java#L406).

Thanks for your work on this very useful package.