When job.spec.completions is nil, only
one task needs to succeed for the job to succeed,
and parallelism can be scaled freely during runtime.
Added tests.
Release Note:
This causes two minor changes to the API.
First, unset parallelism previously was defaulted to be
equal to completions. Now it always defaults to 1 if unset.
Second, having parallelism=N and completions unset would previously
be defaulted to 1 completion and N parallelism.
(this is not something we expect people to do, though)
Now, no defaulting occurs in that case, and the job's
behavior is different (any completion causes success).
All external types that are not int64 are now marked as int32,
including
IntOrString. Prober is now int32 (43 years should be enough of an initial
probe time for anyone).
Did not change the metadata fields for now.
