Replaced dead links with correct ones

Openstack API Quick Start had two dead links in "send
API request" section. The dead links were Identity API
and compute APIs and Extensions. Replaced the dead links
with the new Identity API and compute API links.

closes bug: #1324098

Change-Id: I2c1c5e152230ef2f3e27f5db76bb9a41f48e58ae
Merge "Replaced dead links with correct ones"