Update python-socketio & python-engineio to latest #2591

[phillxnet]

Raise pinned versions to latest available:

Includes:

• Revised nginx reverse proxy for data_collector app.
• Replace gevent-websocket with simple-websocket.
• Replace gevent for regular Python threads in socketio.Server.

Fixes #2591

Requires resolution of / depends upon: rockstor/rockstor-jslibs#36

[phillxnet]

Testing

An rpm built with this proposed change pre-merged but without the associated (linked) update in the js client in rockstor-jslibs we see, via browser dev tools network (Disable Cache selected), the expected:

"The client is using an unsupported version of the Socket.IO or Engine.IO protocols"

With example 404 URLs listed as follows:

https://rleap15-5.lan/socket.io/?EIO=3&transport=polling&t=Oip1gWz

Which indicate that our prior client is attempting to use version 3 of the protocol (?EIO=3). We expect to see ?EIO=4 once our client js is updated in testing branch of rockstor-jslibs.

Consequently we have much depleted header info on all pages and the Dashboard page has the following non-functional widgets:

• Disk Activity
• CPU
• Memory
• Network

All of which depend on websockets to have their info streamed to them.

[phillxnet]

Testing post jslibs fix

Post having the newest jslib socket.io client in place in rockstor-jslibs testing branch we now have full function of our prior detailed widgets and websocket streamed header info (kernel version uptime etc).

A further tests was to ensure our desktop maintain activity during a Web-UI initiated system update (upstream updates). In some development incarnations we had blocking behaviour where the dashboard would freeze during this event.

[phillxnet]

@FroggyFlox & @Hooverdan96 I'll go ahead and pop this one in to ease our other ongoing concerns re updating dependencies. All looks to be behaving as before and we have simpler dependencies. With a key reduction here being the removal of our dependency on gevent-websocket. We have some refinement to do as-yet re allowed clients etc but we can address those as we morph our underlying technologies to using more django native ones. But that, in turn, depends on the following Milestone: https://github.com/rockstor/rockstor-core/milestone/24