ThreatMapper doesn't work correctly with podman and podman-compose

**Describe the bug**
Running ThreatMapper within a podman environment fails looking for Docker endpoints. podman-compose starts up instances, but internally the containers are looking for Docker endpoints and seemingly fail.

```
ERRO: 2022/02/08 11:53:39.832129 docker registry: cannot connect to Docker endpoint
```

**To Reproduce**
Steps to reproduce the behavior:
1. `yum -y install docker` (on a CentOS/RHEL/Rocky 8.x box)
2. `pip3 install podman-compose`
3. `podman-compose -f docker-compose.yml up --detach` - Be sure to pick the docker locations, ThreatMapper isn't inside RedHats registry
4. `podman logs deepfence-discovery` as an example

**Expected behavior**
ThreatMapper should work within podman environments just as well as docker environments

**Components/Services affected**

- [ ] UI/Frontend
- [x] API/Backend
- [ ] Agent
- [x] Deployment/YAMLs
- [ ] CI/CD Integration
- [ ] Other (specify)