mkpidlock: close update loop in error path

[IanButterworth]

No description provided.

[IanButterworth]

I was able to reproduce #51901 on this branch

[vtjnash]

(This is why I wish we could bind a resource to a Task, so that one it ends that resource is implicitly also closed. Channels can do that, but not other resources. Although wait(proc) does not throw errors, so this should be unimportant)

[IanButterworth]

Although wait(proc) does not throw errors

But wait(proc) can be interrupted

julia> begin
       wait(run(`julia -e "sleep(10)"`, wait=false))
       println("here")
       end
^CERROR: InterruptException:
Stacktrace:
 [1] poptask(W::Base.IntrusiveLinkedListSynchronized{Task})
   @ Base ./task.jl:974
 [2] wait()
   @ Base ./task.jl:983
 [3] wait(c::Base.GenericCondition{Base.Threads.SpinLock}; first::Bool)
   @ Base ./condition.jl:130
 [4] wait
   @ ./condition.jl:125 [inlined]
 [5] wait(x::Base.Process)
   @ Base ./process.jl:661

I can still trigger #51901 on this PR though