Install git in devel dockerfile
Install git in devel dockerfile

looks like git is not installed by default
in v15 base image.This PR installs the
git which is required to make containerized
build.

set GO111MODULE=on in dockerfile

we need to set GO111MODULE=on to fix
"build flag -mod=vendor only valid when using modules"
issue

Signed-off-by: Madhu Rajanna <60fbf37a92c2a0908e31296d18dadbec5a4dae17@gmail.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi