simplifies stderr filtering in vagrant_ssh_cmd def
simplifies stderr filtering in vagrant_ssh_cmd def

The former approach was too clever by half, and caused
more problems than it solved. The new approach simply
dumps stderr (most of which is just "Connection closed"
messages, even on success) and the exit code is checked
later for sanity.

chadmiller/securedrop,jaseg/securedrop,pwplus/securedrop,garrettr/securedrop,conorsch/securedrop,ehartsuyker/securedrop,jaseg/securedrop,pwplus/securedrop,micahflee/securedrop,micahflee/securedrop,ehartsuyker/securedrop,pwplus/securedrop,ageis/securedrop,ageis/securedrop,kelcecil/securedrop,conorsch/securedrop,ageis/securedrop,jrosco/securedrop,kelcecil/securedrop,chadmiller/securedrop,chadmiller/securedrop,ehartsuyker/securedrop,jaseg/securedrop,conorsch/securedrop,heartsucker/securedrop,heartsucker/securedrop,micahflee/securedrop,jaseg/securedrop,jaseg/securedrop,pwplus/securedrop,micahflee/securedrop,pwplus/securedrop,garrettr/securedrop,jaseg/securedrop,kelcecil/securedrop,ehartsuyker/securedrop,kelcecil/securedrop,jrosco/securedrop,jrosco/securedrop,kelcecil/securedrop,heartsucker/securedrop,heartsucker/securedrop,kelcecil/securedrop,pwplus/securedrop,conorsch/securedrop,ehartsuyker/securedrop,ageis/securedrop,chadmiller/securedrop,jrosco/securedrop,chadmiller/securedrop,jrosco/securedrop,garrettr/securedrop,chadmiller/securedrop,garrettr/securedrop,heartsucker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,jrosco/securedrop