Fix the condition expression for ssl_insecure

In the existing code, self.ssl_insecure is a string. If insecure
option is set in nova api-paste.ini, whatever it is 'true' or
'false', kwargs['verify'] will become False. This commit corrects
the condition expression. This patch is backported from
https://review.openstack.org/#/c/113191/

Change-Id: I91db8e1cb39c017167a4160079846ac7c0663b03
Closes-Bug: 1353315
Merge "Fix the condition expression for ssl_insecure"