Fix rabbit_max_retry

First, the configvar is defined as a StrOpt. This means that the check
against the integer retry_attempts will fail.

Secondly, rabbit_max_retries is tested as a boolean before comparing
against retry_attempts. With the value 0, this would be false and the
setting rabbit_max_retries=0 would actually retry indefinitely, which is
not the obvious behavior. This patch will make the default not to
retry at all (which was the implied, but not actual, behavior)

Fixes bug 1152866

Change-Id: Ic39d708f0294fc5d919cb2a5d9fae532128ef17e
Fix scrubber and other utils to use log.setup().

scrubber and other utils call config.setup_logging(),
which does not read the 'default_log_levels' config option.
Fix this problem by calling log.setup(), just like what
glance-api and glance-registry do.

Per John Bresnahan's comment, made the change to check
the existence of log conf file in oslo-incubator code.
Refer to https://review.openstack.org/#/c/24230/

Change-Id: I4a53d74c4cd8274a3174b246207a6ed76c5e31c6
Fixes: bug #1153432
Merge "Fix scrubber and other utils to use log.setup()."
Merge "Fix rabbit_max_retry"