Add log output of x-openstack-request-id from nova

This patch enables heat to output
'x-openstack-request-id'/'x-compute-request-id'
of nova's responses to the log.

DocImpact: There is a new novaclient configuration
option 'http_log_debug' in heat.common.config

Change-Id: Id085af411c6d4ceddce1a75022c4baec9a8210ce
Closes-bug: #1329612
Merge "Add log output of x-openstack-request-id from nova"