use Functest tempest_custom test cases to run all Ipv6 test cases

use Functest tempest_custom test cases to run all Ipv6 test cases

JIRA: DOVETAIL-401

1. modify all Ipv6 test cases, change tempest_smoke_serial/tempest_full_parallel
   into tempest_custom, add ID of each sub-testcases.
2. Some sub-testcases in ipv6.tc002, ipv6.tc003, ipv6.tc004 and ipv6.tc005 can not
   be found in the full tempest test case list.
2. disable testcases' script_result_acquired to enable tempest_custom run multiple times.
3. use build_tag-testcase_name(such as daily-master-79a6e392-28bb-4c40-9d88-a03bed99da2d-dovetail.ipv6.tc025)
   as the unique ID of each testcase.
4. comment out the progress bar, because it has some problems when print the report text.
5. Functest has changed the TEST_DB_URL from http://<testapi>:<port>/apv/v1 to
   http://<testapi>:<port>/apv/v1/results.
6. Functest has changed the TEST_DB_URL to file://<file_path>/<file_name>.
   see https://gerrit.opnfv.org/gerrit/#/c/33511/

Change-Id: I524f6702377f215f526158214842481eb44565be
Signed-off-by: xudan <xudan16@huawei.com>