Change nginx configuration

Change nginx configuration

Since landing page have changed from reporting2 to testing,
the nginx configuration need some adoption.

If the pre url change again, we need to config the base_url when start
our docker container. For example:
    docker run -itd -p 8084:8000 -e SERVER_URL testresults.opnfv.org/xxx/api opnfv/reporting:latest

Change-Id: If3c9f9af76fcfc8047b5b9559fcc8bd45740d4d2
Signed-off-by: chenjiankun <chenjiankun1@huawei.com>