Due to the 'glanceclient.common.utils.add_req_id_to_object' decorator,
an instance of 'glanceclient.common.utils.RequestIdProxy' is returned
for most calls in glanceclient. If we wish to compare to None, we have
to compare the contents of this wrapper and not the wrapper itself.

Unit tests are updated to highlight this.

Change-Id: I7dadf32d37ac2bda33a92c71d5882e9f23e38a82
Closes-Bug: #1736759

Currently client is contacting glance service even if the
caller has niether specified any redirection nor '--file'
option. This unnecessary request although isn't causing
any critical issues but can be avoided by simply doing
input validation first.

TrivialFix

Change-Id: I841bebeda38814235079429eca0b1e5fd2f04dae

Hiding the unhandled exception in the test with a failure makes it
harder to debug the problem. Let them pass unhandled so the test reports
an ERROR instead of FAILURE.

Change-Id: I4e435a6d276fdf161dac28f08c2c7efedd1d6385
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

Some of tests use different method of assertTrue(isinstance(A, B))
or assertEqual(type(A), B). The correct way is to use
assertIsInstance(A, B) provided by test tools.

Change-Id: Ibb5e5f848c5632f7c1895c47b8c1a938f2c746c3

This allows us to pass in a global_request_id in the client
constructor so that subsequent calls with this client pass that to the
servers. This enables cross project request_id tracking.

oslo spec I65de8261746b25d45e105394f4eeb95b9cb3bd42

Change-Id: Iea1e754a263a01dae5ed598fdda134394aff54b0

Downloading image with --progress fails with "RequestIdProxy object is
not an iterator". This is because to display download progress
VerboseFileWrapper in progressbar requires object of IterableWithLength,
but after support of returning request-id [1] to caller it returns
RequestIdProxy object which is wrapped around IterableWithLength
and response.

To resolve this issue overridden next and __next__ methods in
RequestIdProxy so that it can act as iterator for python 2.x
and 3.x as well.

[1] 610177a779b95f931356c1e90b05a5bffd2616b3

Closes-Bug: #1670464
Change-Id: I188e67c2487b7e4178ea246f02154bbcbc35a2b1