The upstream of github.com/genuinetools/amicontained switched to the
container runtime detection via github.com/genuinetools/bpfd/proc,
which supports a larger range of container runtimes. With this change
(among others) Podman can be detected correctly.
Fixes#1501.
* Upgrade go.mod file
* Upgrade travis file
* Run rm -rf vendor && go mod tidy && go mod vendor to upgrade vendor/modules.txt according to golang 1.14
* Upgrade golangci-lint version
* add util.GetFSFromLayers
* GetFSFromImage delegates to GetFSFromLayers
* add FSOpts and FSConfig for GetFSFromLayers
* add tests for GetFSFromLayers
* add gomock for test support
* add mock_v1 for layers