Renaming ironicclient exceptions in nova driver

Since ironicclient uses exceptions from common code(
0f6419015c5f03448689ffe7c75ff3bdb5f19c08), names of several exceptions
changed. New names should be used in nova driver.

Related to bp common-client-library-2

Change-Id: I717aec8667a68c173f571ecc7d992b9fca3896c3
Update dev quickstart guide for ephemeral testing

Devstack now supports the IRONIC_VM_EPHEMERAL_DISK variable
which allows the user to specify the size of the ephemeral
disk partition. This change documents how to use this variable
to boot an instance with ephemeral storage.

Change-Id: Idd3bf8c4c63d32a8ed2bacd37ba642eb70f709db
Using system call for downloading files

Using system call `sendfile` for downloading files using glance
image service. It's more efficient than passing the entire image
through Python `shutil`.

Change-Id: Ic36c593538fd97d3ac02d3ad77feebcfdb9f1868
Closes-Bug: #1199522
Fix wrong usage of mock methods

There is no assert_not_called() method in mock, as described here:
https://code.google.com/p/mock/issues/detail?id=159
Fix the call to use the mock.called attribute instead.
This patch also uses right method assert_called_once_with instead
of assertCalleOnceWith.

Change-Id: Idc0125db73cd11707ce885813174ec38535dc501
Merge "Update dev quickstart guide for ephemeral testing"
Merge "Fix wrong usage of mock methods"
Merge "Renaming ironicclient exceptions in nova driver"
Merge "Using system call for downloading files"
Remove all mostly untranslated PO files

We now only import PO files that are at least 75 % translated,
so we can delete now all other PO files. The patch only
removes the mostly untranslated files. Once a file becomes mostly
translated, the bot will import it again.

This removes all languages besides en_US and en_AU.

Change-Id: Ie5d98c0f56d3f79dee6453bacca7b76c110d249e
Closes-Bug: #1317794