FsShell forces creation of default filesystem object and incorrectly uses default filesystem in some places

i was trying do fs -ls operations on s3n filesystem uris (which was not configured as my default filesystem - the default filesystem was not bought up). these operations failed since they always tried to open the default filesystem (error: ""Bad connection to FS. command aborted."). but the default filesystem is not required in these cases at all.

the code also shows that the default filesystem is used in certain places (instead of the filesystem of the uri). for instance:

copy(String argv[], ...) { ...
Path dst = new Path(dest);
if (!fs.isDirectory(dst)) {

there are some other places as well.