Issue-ID: PORTAL-913 optimization in git clone using --depth

optimize the git clone using --depth flag in term of size of clone
and also in term's of time taken to fetch the files and commit history
of whole repository .

Respective issue is created at https://jira.onap.org/browse/PORTAL-913

More detail can be found at blog
https://www.atlassian.com/git/tutorials/big-repositories

Signed-off-by: Pratik Raj <rajpratik71@gmail.com>
Change-Id: I79c7dfb928115ac438738b9bda1017dd6549560f