test update of shared arrays in a @parallel for

[amitmurthy]

ref issue #14664

[tkelman]

Thanks!

[amitmurthy]

Both CI failures are unrelated.

[tkelman]

AppVeyor failure was in subarray? https://ci.appveyor.com/project/StefanKarpinski/julia/build/1.0.12995/job/xo40ge8as3rvxxmy
#14860 had a very similar looking failure https://ci.appveyor.com/project/StefanKarpinski/julia/build/1.0.12994/job/6s4b6p15vwwhfrtb

In case anyone restarts the travis build and the log vanishes, here's the travis failure:

From worker 7:       * float16              Test Failed
    From worker 7:    Expression: round(Int,Float16(x)) == round(Int,x)
    From worker 7:     Evaluated: 0 == 1
<snip>
Exception running test float16 :
On worker 7:
LoadError: There was an error during testing
 in record at ./test.jl:317
 in do_test at ./test.jl:215
 [inlined code] from ./essentials.jl:80
 in include_string at ./loading.jl:371
 in include_from_node1 at ./loading.jl:420
 [inlined code] from ./util.jl:179
 in runtests at /tmp/julia/share/julia/test/testdefs.jl:7
 in #16 at /tmp/julia/share/julia/test/runtests.jl:36
 in run_work_thunk at ./multi.jl:714
 [inlined code] from ./multi.jl:1010
 in #253 at ./task.jl:60
while loading /tmp/julia/share/julia/test/float16.jl, in expression starting on line 40
ERROR: LoadError: Some tests exited with errors.
 in #11 at /tmp/julia/share/julia/test/runtests.jl:64
 in cd at ./file.jl:47
 in include at ./boot.jl:264
 in include_from_node1 at ./loading.jl:417
 in process_options at ./client.jl:244
 in _start at ./client.jl:300
while loading /tmp/julia/share/julia/test/runtests.jl, in expression starting on line 13