fix #150: remove ALL matching allowedHosts items

[groovecoder]

I couldn't actually reproduce the original state of #150. I.e., I think it was caused by a previous bug in the add-on that added multiple items of the same host into the allowedHosts array. That bug has since been closed, but those of us (like @pdehaan) who had the add-on running before it was closed likely got into a state where we had multiple items of the same host in our allowedHosts array.

To fix, I wrapped the allowedHosts.splice call in a do...while loop to clear out ALL matching items from the allowedHosts array.

To test:

1. Run the add-on and disable protection for a few different sites.
2. Go back to at least one of the sites where you disabled protection, and re-enable it.

Verify:

Refresh each of the sites and verify that their protection state is what you expect. I.e., the disabled sites are still disabled, and the re-enabled site(s) is enabled.

[coveralls]

Coverage decreased (-0.3%) to 45.94% when pulling 06f7691 on re-enable-clear-any-allowsHosts-items-150 into 5d74775 on master.

[coveralls]

Coverage decreased (-0.4%) to 45.842% when pulling 06f7691 on re-enable-clear-any-allowsHosts-items-150 into 5d74775 on master.

[pdehaan]

👍
LGTM. I don't think I've encountered the error again, since reporting this. So it's hard to verify locally.

[groovecoder]

In that case, I think I'd actually like to close this PR without merging to avoid any potential knock-on effects of this change; but leave the branch on GitHub in case it comes up again.