Place config_functest.yaml outside the functest repo

Place config_functest.yaml outside the functest repo

If config_functest.yaml is given it will be placed in:
    /home/opnfv/functest/conf/config_functest.yaml
If not given:
   copy default from repo to that location

Change-Id: I816bf5ccf8e0a5b8ebde2a0ab924657533f49127
Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>
(cherry picked from commit 00b51ffe114702ce207aa7ba2e40f01984c0c57c)