pipelines: Input variables at app stanza not overriding

[briancain]

Describe the bug

When running waypoint pipeline run with an input var override defined on the CLI, it doesn't look like that input var gets set properly from the override:

brian@ubuntu:waypoint-tetris λ waypoint pipeline run -var="tag=1" marathon                                                                                 ±[main]

» Running pipeline "marathon" for application "tetris"
✓ Pipeline "marathon" has started running. Attempting to read job stream sequentially in order
✓ 1 steps detected, run sequence 2
...
...
» Building tetris...
✓ Running build v4
✓ Building Docker image with kaniko...
✓ Testing registry and uploading entrypoint layer
✓ Executing kaniko...
 │ INFO[0001] Retrieving image manifest nginx:stable
 │ INFO[0001] Returning cached image manifest
 │ INFO[0001] Executing 0 build triggers
 │ INFO[0001] Unpacking rootfs as cmd COPY ./public/ /var/www requires it.
 │ INFO[0004] COPY ./public/ /var/www
 │ INFO[0004] Taking snapshot of files...
 │ INFO[0004] COPY ./nginx.conf /etc/nginx/conf.d/default.conf
 │ INFO[0004] Taking snapshot of files...
 │ INFO[0004] Pushing image to localhost:38817/tetris:latest
 │ INFO[0005] Pushed image to 1 destinations
✓ Image pushed to '<contianer_registry>/tetris:latest'
...
...
# the variable used
 tag               | latest                                        | string    | default

Steps to Reproduce

Run a pipeline via the CLI with a CLI input var override for a variable defined inside an app {} stanza. See that it uses the default rather than the override.

variable "tag" {
  default     = "latest"
  type        = string
  description = "Image tag for the image"
}
app "tetris" {
  build {
    use "docker" {
    }

    registry {
      use "docker" {
        image    = var.image
        tag      = var.tag
        username = var.registry_username
        password = var.registry_password
        local    = var.registry_local
      }
    }
  }
...
...
}

Expected behavior

The override should be respected and used for the pipeline run.

Waypoint Platform Versions
Additional version and platform information to help triage the issue if
applicable:

• Waypoint CLI Version: main at b7c98b1
• Waypoint Server Platform and Version: n/a
• Waypoint Plugin: n/a

Additional context
Add any other context about the problem here.