Use testr instead of nosetest

This patch removes the dependency on nosetest and uses testrepository as
a test runner. There are some advantages behind this change:

    - Better tests execution
    - Better tests concurrency
    - Less dependencies

Change-Id: I1985bdf03137d32a0774321d8dec5cb015dc9d2f
Enforce size verification on content-length

Closes-Bug: #1261579

Previously, Marconi used to enforce the message and queue size limit on
the resource itself. In the case of a Message, it'd verify that the
message body wouldn't exceed the message size limit. This enforcement
has been moved, by this patch, up to the request size.

For both cases, the content_length is required to be smaller than the
size limit configured by the service admin. None of the default values
were modified.

Change-Id: I06e28acaac234242a40cd2afafb12be067851c20
Merge "Use testr instead of nosetest"
Merge "Enforce size verification on content-length"