fix(uid): set default container uid (backport #11)

[mergify]

Fixes #10
Related to cryostatio/cryostat-operator#969

To test using the Cryostat Operator on OpenShift:

1. export OPENSHIFT_OAUTH_PROXY_IMG=quay.io/andrewazores/openshift-oauth-proxy:uid-1
2. Build and deploy Operator in default namespace
3. Create Cryostat CR in default namespace with that as the target namespace: TARGET_NAMESPACES=$(oc project -q) make create_cryostat_cr
4. Ensure that the Cryostat Deployment is created and Pod becomes Ready
5. Ensure that the auth-proxy container within the Pod is running the image above (built from this PR)
6. Ensure that the auth-proxy container is running normally and Cryostat can be accessed by logging in through the proxy as usual

Or to test using Cryostat Helm on OpenShift:

1. Switch to default project (oc project default)
2. Deploy with existing upstream images to reproduce the bug: $ helm install cryostat --set authentication.openshift.enabled=true --set core.route.enabled=true ./charts/cryostat/
3. helm uninstall cryostat
4. Deploy with this PR's auth-proxy rebuild: $ helm install cryostat --set openshiftOauthProxy.image.repository=quay.io/andrewazores/openshift-oauth-proxy --set openshiftOauthProxy.image.tag=uid-1 --set authentication.openshift.enabled=true --set core.route.enabled=true ./charts/cryostat/
5. Check OpenShift console to ensure that the Pod becomes ready, the container is running the expected image, etc.
6. Go to Cryostat Route and ensure that it's possible to log in and access Cryostat through the proxy

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   This is an automatic backport of pull request fix(uid): set default container uid #11 done by Mergify.