hdfs `delete` fails where `rm` succeeds. Also `maxdepth` is unspported.

In the spec, delete is supposed to be an alias for rm. However this fails for hdfs.

fs = fsspec.filesystem("hdfs")
fs.delete("hdfs:///user/f4hy/test/testfile.txt")
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-16-9390bf0d502b> in <module>
----> 1 fs.delete("hdfs:///user/bfahy2/bin/test2.py")

~/.local/lib/python3.7/site-packages/fsspec/spec.py in delete(self, path, recursive, maxdepth)
   1136     def delete(self, path, recursive=False, maxdepth=None):
   1137         """Alias of :ref:`FilesystemSpec.rm`."""
-> 1138         return self.rm(path, recursive=recursive, maxdepth=maxdepth)
   1139 
   1140     def upload(self, lpath, rpath, recursive=False, **kwargs):

TypeError: rm() got an unexpected keyword argument 'maxdepth'

while rm works fine, but only without maxdepth

fs.rm("hdfs:///user/f4hy/test/testfile.txt") # ok
fs.rm("hdfs:///user/f4hy/test/testfile.txt", maxdepth=1) # errors

The pyarrow implementation is just passing rm to the pyarrow filespec, but it doesnt exactly match up with fsspec.

We should make sure all options in the fsspec are supported, or if not at at least spew a better error.

Start with the FilesystemSpec.delete method shown in spec.py and trace the HDFS and PyArrow rm implementations. Check how recursive and maxdepth are handled for both rm and delete, then verify that supported options behave consistently or produce a clear error when unsupported.