Make SSH key generation more robust.
Make SSH key generation more robust.

Do not try and predict whether we will be able to create a key. Instead
try and create one and capture failure if it happens.

Closes #803

php-censor/php-censor,corpsee/php-censor,php-censor/php-censor,corpsee/php-censor,corpsee/php-censor,php-censor/php-censor