init_blocks needs to be 0 for kubernetes provider

[ZhuozhaoLi]

When init_blocks is not set to 0 with kubernetes providers, funcx-endpoint raises the following exception:

2020-09-01 20:28:46.249 interchange:254 [ERROR]  Caught exception
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/funcx_endpoint/executors/high_throughput/interchange.py", line 252, in __init__
    self.load_config()
  File "/usr/local/lib/python3.6/site-packages/funcx_endpoint/executors/high_throughput/interchange.py", line 301, in load_config
    self.scale_out(self.config.provider.init_blocks)
  File "/usr/local/lib/python3.6/site-packages/funcx_endpoint/executors/high_throughput/interchange.py", line 802, in scale_out
    internal_block = self.config.provider.submit(launch_cmd, 1)
TypeError: submit() missing 1 required positional argument: 'task_type'

It should either raise a more informative exception to the user or ignore init_blocks for k8s.