Update git submodules
* Update docs/submodules/dovetail from branch 'master'
- Switch to OPNFV Fraser release
1. Use Functest Fraser docker images whose tag is fraser
2. Use Yardstick stable docker images
3. Functest fraser has moved testcases.yaml file from functest/ci to xtesting/ci
4. Functest fraser has removed 'functest env prepare' command
5. Functest uses rally to execute osinterop test cases
instead of refstack_client
Change-Id: I81ebefe6ea959ca77c2c87f1d75ef56ac18c165f
Signed-off-by: xudan <xudan16@huawei.com>