Backport fix in test/simple/test-child-process-spawn-typeerror.js from v0.12 to v0.10

[misterdjules]

#8928 fixes an issue that was exposed by a merge from v0.10 to v0.12. However, the same issue is present in v0.10 too.

Once the merge from v0.10 to v0.12 is done, we should backport #8928 to v0.10.

The Right Way to do it would be to fix it in v0.10 first and then merge it into v0.12, but in this case a merge from v0.10 to v0.12 is already in progress, and we're close to be done with it, so we don't want to add more noise and complication.

[cjihrig]

@misterdjules assigning this to myself.

[misterdjules]

@cjihrig Thanks!