bug-fix: no percentage calculated in verify ci

JIRA: BOTTLNECK-219

It seems that ci verify job could not get the coverage percentage
for empty directory. This patch is to add __init__ file for the
empty directory to avoid the empty check.
note that offline test does not has this issue

Change-Id: I67ce149438516429f7285e9424a57439b188c070
Signed-off-by: Yang Yu <Gabriel.yuyang@huawei.com>