[config] Use temporary folder during unit tests
[config] Use temporary folder during unit tests

The new minimalist ifmap server needs SSL certificate and key to expose
the IF-MAP v2 API to the control nodes. By default it uses the folder
'/var/lib/contrail/api-server/ifmap-cert/' which could not be  accessible
in certain situations. That fix uses the system temporary folder.

Change-Id: I214e07452d039049d9485e7f6e8f4821d4eb4a6a
Closes-Bug: #1662348

eonpatapon/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller