amazon-ebssurrogate not able to lookup source volume id when using spot instances

_This issue was originally opened by @sergey-safarov as hashicorp/packer#9347. It was migrated here as a result of the [Packer plugin split](https://github.com/hashicorp/packer/issues/8610#issuecomment-770034737). The original body of the issue is below._

---

#### Overview of the Issue
Issue related to https://github.com/hashicorp/packer/issues/8777 and reproduced on current master.

When using spot instances with the `amazon-ebssurrogate` builder, the builder is not able to lookup the id of the source volume(s). This appears to be because it issues the describe instance call to AWS after it has stopped the EC2 instance, and not before.

#### Reproduction Steps
Try and use spot instances with `amazon-ebssurrogate`, you'll get the following error regardless of the value of `delete_on_termination` in the `launch_block_device_mappings` config:
```
==> amazon-ebssurrogate: 1 error occurred:
==> amazon-ebssurrogate: * Volume ID for device /dev/xvdf not found
==> amazon-ebssurrogate:
==> amazon-ebssurrogate:
```

Simply replacing the `spot_*` configuration options with `instance_type` works.

### Packer version

```
[safarov@safarov-dell intetics]$ packer version
Packer v1.6.0-dev (19e4afa728c02104d2c0571e6c6fb86278009a75)
```

### Simplified Packer Buildfile
**Fails:**
```json
{
"builders": [
{
"ami_name": "packer debug {{ user `BuildTime` }}",
"ami_virtualization_type": "hvm",

"type": "amazon-ebssurrogate",
"spot_instance_types": [
"c5.large",
"c5.xlarge"
],
"spot_price": "auto",

"launch_block_device_mappings": [
{
"volume_type": "gp2",
"device_name": "{{ user `DeviceName` }}",
"delete_on_termination": false,
"volume_size": 20
}
],

"ami_root_device": {
"delete_on_termination": true,
"device_name": "/dev/xvda",
"source_device_name": "{{ user `DeviceName` }}",
"volume_size": 20,
"volume_type": "gp2"
}
}
]
}
```
**Works:**
```json
{
"builders": [
{
"ami_name": "packer debug {{ user `BuildTime` }}",
"ami_virtualization_type": "hvm",

"type": "amazon-ebssurrogate",
"instance_type": "c5.large",

"launch_block_device_mappings": [
{
"volume_type": "gp2",
"device_name": "{{ user `DeviceName` }}",
"delete_on_termination": false,
"volume_size": 20
}
],

"ami_root_device": {
"delete_on_termination": true,
"device_name": "/dev/xvda",
"source_device_name": "{{ user `DeviceName` }}",
"volume_size": 20,
"volume_type": "gp2"
}
}
]
}
```
### Operating system and Environment details

Tested on Linux.

### Log Fragments and crash.log files
```
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [DEBUG] Opening new ssh session
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [DEBUG] starting remote command: rm -f /tmp/script_6506.sh
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [INFO] RPC endpoint: Communicator ended with: 0
2020/06/02 22:13:45 [INFO] RPC client: Communicator ended with: 0
2020/06/02 22:13:45 [INFO] RPC endpoint: Communicator ended with: 0
2020/06/02 22:13:45 packer-provisioner-shell plugin: [INFO] RPC client: Communicator ended with: 0
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [DEBUG] Opening new ssh session
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [DEBUG] starting remote command: rm -f
2020/06/02 22:13:45 packer-builder-amazon-ebssurrogate plugin: [INFO] RPC endpoint: Communicator ended with: 0
2020/06/02 22:13:45 [INFO] RPC client: Communicator ended with: 0
2020/06/02 22:13:45 [INFO] RPC endpoint: Communicator ended with: 0
2020/06/02 22:13:45 packer-provisioner-shell plugin: [INFO] RPC client: Communicator ended with: 0
2020/06/02 22:13:45 [INFO] (telemetry) ending shell
==> amazon-ebssurrogate: * Volume ID for device /dev/sdf not found
==> amazon-ebssurrogate:
==> amazon-ebssurrogate:
==> amazon-ebssurrogate: 1 error occurred:
==> amazon-ebssurrogate: * Volume ID for device /dev/sdf not found
==> amazon-ebssurrogate:
==> amazon-ebssurrogate:
==> amazon-ebssurrogate: Provisioning step had errors: Running the cleanup provisioner, if present...
==> amazon-ebssurrogate: Terminating the source AWS instance...
==> amazon-ebssurrogate: Cleaning up any extra volumes...
==> amazon-ebssurrogate: No volumes to clean up, skipping
==> amazon-ebssurrogate: Deleting temporary security group...
==> amazon-ebssurrogate: Deleting temporary keypair...
2020/06/02 22:14:06 [INFO] (telemetry) ending amazon-ebssurrogate
* Volume ID for device /dev/sdf not found

Build 'amazon-ebssurrogate' errored: 1 error occurred:

* Volume ID for device /dev/sdf not found
2020/06/02 22:14:06 machine readable: error-count []string{"1"}
==> Some builds didn't complete successfully and had errors:

2020/06/02 22:14:06 machine readable: amazon-ebssurrogate,error []string{"1 error occurred:\n\t* Volume ID for device /dev/sdf not found\n\n"}
* Volume ID for device /dev/sdf not found

==> Builds finished but no artifacts were created.

2020/06/02 22:14:06 [INFO] (telemetry) Finalizing.

==> Some builds didn't complete successfully and had errors:
--> amazon-ebssurrogate: 1 error occurred:
* Volume ID for device /dev/sdf not found

==> Builds finished but no artifacts were created.
```