Gyuricska Milán / cloud

This reverts commit 22b41546

Using join method on the nodes list instead of string concatenation. Logging if monitor info unreachable or None in get_monitor_info method.

Each node, which has unreachable monitor info shown in one error message.

The page now loads when the node can't reach the monitor info values e.g. cpu percent. It gets a default value 0. And if a node's monitor info unreachable shows
an error message.

If the monitor info can't get the values, the values get default 0.

django.db.models.field.subclassing.SubfieldBase removed: https://docs.djangoproject.com/en/1.11/releases/1.10/#features-removed-in-1-10
New field classes require to call full_clean() method on Models, because the to_python() din't call automatically.
Related docs: https://docs.djangoproject.com/en/1.11/releases/1.8/#subfieldbase

dashboard, vm: fix user handling i tests, new Origin type cannot implicit convert to str, fix redirect_chain in 2FA tests, importing vm operation in __init_.py is unnecessary and and brokes the application

closes #432

also display the queue statuses on node detail

Closes #426

closes #443

and disable the remove button for non ops

closes #437

closes #420

closes #410

closes #375

closes #373

common: fix issue #228 (return value of Operation._operation (if any) could be the result of the activity"

closes #228

closes #97