Add integration test for running containers after actual soci convert

[prafgup]

Description of changes:

Followup from here - #1881 (comment)

• Add TestRunAfterConvert in run_test.go to verify that containers can be lazily loaded after soci convert, for both standard and standalone convert modes.

Testing performed:

lima sudo bash -c 'export PATH="$PATH:/root/go/bin" && GO_TEST_FLAGS="-run TestRunAfterConvert -count=1" make integration'
cd cmd/ ; GO111MODULE=auto go build -o /Volumes/git/prafulg/soci-snapshotter/out/soci-snapshotter-grpc  -ldflags '-X github.com/awslabs/soci-snapshotter/version.Version=90d55a03.m -X github.com/awslabs/soci-snapshotter/version.Revision=90d55a033adc7565dfefac7258cf25fbb7b63697.m  -s -w '  ./soci-snapshotter-grpc
cd cmd/ ; GO111MODULE=auto go build -o /Volumes/git/prafulg/soci-snapshotter/out/soci  -ldflags '-X github.com/awslabs/soci-snapshotter/version.Version=90d55a03.m -X github.com/awslabs/soci-snapshotter/version.Revision=90d55a033adc7565dfefac7258cf25fbb7b63697.m  -s -w '  ./soci
integration
SOCI_SNAPSHOTTER_PROJECT_ROOT=/Volumes/git/prafulg/soci-snapshotter
=== RUN   TestRunAfterConvert
=== RUN   TestRunAfterConvert/standard_convert
--- PASS: TestRunAfterConvert/standard_convert (4.75s)
=== RUN   TestRunAfterConvert/standalone_convert
--- PASS: TestRunAfterConvert/standalone_convert (5.23s)
--- PASS: TestRunAfterConvert (11.19s)
PASS
ok      github.com/awslabs/soci-snapshotter/integration 127.671s

DONE 3 tests in 127.671s

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[prafgup]

Hey @sondavidb wondering if releasing a new tagged version is being evaluated internally for this? Ref - #1881 (comment)
(would appreciate a release so we can start consuming the release instead of building from commit)

[sondavidb]

LGTM!

wondering if releasing a new tagged version is being evaluated internally for this?

We have another pretty big PR (#1844) that I think customers would also appreciate having functionality for. After this is merged I personally would like to get one out ASAP. But again, I'm not allowed to promise anything. (I don't see why we can't, though.)

[sondavidb]

Closed and reopened just to get checks running. (The button disappeared for me for some reason...)