Fix typo in checking for ignore_nonexisting in LocalTransport

[mbercx]

Thanks for the contribution @MichaelGoulding! I can see how the fact that the method looks for ignore_noexisting in the kwargs is problematic... Especially since other methods use an ignore_existing input (thankfully not popping kwargs). I'm a bit apprehensive towards fixing this directly, however, since users may be relying on the (unintuitive/incorrect) ignore_noexisting input and hence this would technically be a backwards-incompatible change.

I'll work on a deprecation path instead, and also add some more tests to make sure we don't break existing behaviour.

[MichaelGoulding]

@mbercx The issue is that I when I switched an existing workflow that was using SshTransport to instead use LocalTransport, the workflow no longer worked. Perhaps LocalTransport could support both names for now?