Over-escaping in drush ssh when using compound statement

[weitzman]

from @mishac in #drush

$ drush -v @dev ssh "cd .. && pwd"
[info] Executing: ssh -o PasswordAuthentication=no USER@HOST 'cd /var/www/vhosts/HOST/dev/web && cd .. '\''&&'\'' pwd' 

Note odd escaping of &&

We may need to assume already-escaped in this case.

[greg-1-anderson]

I think we need to presume that if there is only one parameter to ssh, then it is pre-escaped.

I'm not sure exactly where is the best place to insert that assumption. I think that if the Drush ssh command did the check and wrapped its only parameter in Shell::preEscaped(), it would work.