Unable to remove filesystem's description

[v-soni11]

Issue: Unable to remove filesystem's description by providing empty string

steps to reproduce:

>>> from storops.unity.resource import nfs_share
>>> from storops import UnitySystem
>>>
>>> conn = UnitySystem('xx.xx.xx.xx', 'username', 'password', verify=False)
>>>
>>> nas_obj = conn.get_nas_server(name="nas_server")

>>> fs = conn.get_filesystem(name="vvk_fs", nas_server=nas_obj)
>>> fs.description
'test'
>>> fs.modify(description='')
<storops.unity.resp.RestResponse object at 0x7f8d78cb1278>
>>> fs = conn.get_filesystem(name="vvk_fs", nas_server=nas_obj)
>>> fs.description # should be empty '' instead of 'test'
'test'

[yong-huang]

Root caused, will fix it.

[yong-huang]

Fixed in #335

[v-soni11]

Verified. Its Fixed Now