Support volume_readonly_update using XML format

Almost all API support JSON and XML format together,
But this API does not support xml format.
In the request of xml format,
the type of parameter "readonly" in the body is string.
In the request of JSON format,
the type of parameter "readonly" in the body is bool.
But the code only support bool, not support string.
This branch is to solve this problem.

Closes-bug #1244848

Change-Id: I7f2b09a0063df9daad3fdd09789f8e19c43b0aa3
(cherry picked from commit 76497ce9607df98e9e10fb1de1b6e607432f731b)
Catch ImageBusy exception when deleting rbd volume

If we try to delete an rbd volume that has 'watchers' on it
i.e. client connections that have not yet been closed
possibly because a client crashed, the remove() will throw an
ImageBusy exception. We now catch this exception and raise
VolumeIsBusy with a useful message.

If the volume delete fails in this way it will now stay as
'available' instead of going to 'error_deleting' so that the
delete can be retried (since it is expected to work on a
retry after waiting for the connection to timeout).

Change-Id: I5bc9a5f71bdb0f9c5d12b5577e68377e66561f5b
Closes-bug: 1256259
(cherry picked from commit f31d62a178a370ae9d736c09a3186ea9a3c92ee3)
Don't raise MySQL 2013 'Lost connection' errors

Closes-bug: #1276510

Although this code error is part of the `ping_listener` tests, it was
missing from the list of known - and ignored - connection errors.

The code error 2013 refers to a connection lost during a query, see:
https://dev.mysql.com/doc/refman/5.0/en/error-messages-client.html#error_cr_server_lost

Without this error code, the session won't try to reconnect to mysql,
which makes `max_retries` useless.

Change-Id: If2667cf83ac656666ffe00aa90e3454516b080db
Merge "Catch ImageBusy exception when deleting rbd volume" into stable/havana
Merge "Don't raise MySQL 2013 'Lost connection' errors" into stable/havana
Merge "Support volume_readonly_update using XML format" into stable/havana
Merge remote-tracking branch 'upstream/stable/havana' into stable/havana