fix: adds signal handling and proper clean up

[faiq]

What problem does this PR solve?:

this solves removing temp directories that kib creates without signal handling the defer to clean the temporary directory we create, littering the users disk.

Which issue(s) does this PR fix?:

• https://jira.d2iq.com/browse/D2IQ-NUMBER

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[faiq]

This cleans up everything now

06:00 PM  fraza @ Linux-PC1RG42G  ~/go/src/github.com/mesosphere/konvoy-image-builder  faiq/signal-handling? 
$ ./bin/konvoy-image-wrapper build aws images/ami/rhel-88.yaml  
2024/10/17 01:01:11 writing new packer configuration to work/rhel-8.8-1729126871-qajKU
2024/10/17 01:01:11 starting packer build
^Ccontext canceled
error encountered: cmd failed exit status 1

06:01 PM  fraza @ Linux-PC1RG42G  ~/go/src/github.com/mesosphere/konvoy-image-builder  ⏎ 1  faiq/signal-handling? 
$ docker ps
CONTAINER ID   IMAGE                           COMMAND                  CREATED        STATUS             PORTS     NAMES
865bc2685341   moby/buildkit:buildx-stable-1   "buildkitd --allow-i…"   2 months ago   Up About an hour             buildx_buildkit_konvoy-image-builder0