jobwait(): fix race if job exits before waiting on it

Problem:  If a job exits while waiting on another job, the on_exit
          handler is queued but f_jobwait() skips it.
Solution: Always do process_wait(), so that handlers are run during
          f_jobwait().

fix #8302

Test case:
    $ BUSTED_ARGS="--repeat=2000 --no-keep-going" TEST_FILE=test/functional/core/job_spec.lua TEST_FILTER=waiting make functionaltest

Failure example (macOS CI):
    FAILED  test/functional/core/job_spec.lua: jobs jobwait will run callbacks while waiting
    test/functional/core/job_spec.lua:606: Expected objects to be the same.
    Passed in:
    (table: 0x1be77c80) {
      [1] = 'notification'
      [2] = 'wait'
     *[3] = {
       *[1] = 3 } }
    Expected:
    (table: 0x1be77d10) {
      [1] = 'notification'
      [2] = 'wait'
     *[3] = {
       *[1] = 4 } }
    stack traceback:
      test/functional/core/job_spec.lua:606: in function <test/functional/core/job_spec.lua:583

0 files changed, 0 insertions, 0 deletions