'Check if a datastore is usable as per the given mount info.
The datastore is considered to be usable for a host only if it is
writable, mounted and accessible.
:param mount_info: Host mount information
:return: True if datastore is usable'

def _is_usable(self, mount_info):

    writable = (mount_info.accessMode == 'readWrite')
    mounted = getattr(mount_info, 'mounted', True)
    accessible = getattr(mount_info, 'accessible', False)
    return (writable and mounted and accessible)
