[Core] 'sky cancel' failing to terminate first job started with 'sky launch'

[landscapepainter]

Basically, current master branch fails to terminate the job created with sky launch which has job id 1. After launching job with id 1, running sky exec to launch a second job with job id 2 gets successfully terminated with sky cancel. So current sky cancel behaves differently on the job with job id 1 and the ones get ran after.

Repro:
cancel_test.yaml:

workdir: ~/cancel_test

run:
  python3 cancel.py

~/cancel_test/cancel.py:

import time

time.sleep(7200)
print('completed!')

$ sky launch cancel_test.yaml -c mycluster --cloud gcp -y
$ sky cancel mycluster 1
$ ssh mycluster
$ ps aux | grep cancel
root        6612  0.0  0.0  11492  7844 ?        SN   05:14   0:00 python3 cancel.py

This may be the root cause of #3742

Version & Commit info:

• sky -v: PLEASE_FILL_IN
• sky -c: PLEASE_FILL_IN