check if bootstrap-osd exsits before creating the keyring file

Signed-off-by: Dongmao Zhang <dmzhang@suse.com>
Check if ssh command prints "Host key verification failed." error message

"can_connect_passwordless" func will return false if ssh with an exit status
of 255 and a "Host key verification failed." message
Merge pull request #221 from tolbkni/ssh_host_key_error

Check if ssh command prints "Host key verification failed." error message
create a subcommand

Because we might want to specify *what* repo we want to install
remotely (cephdeploy.conf can have a bunch listed)

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
update the docstring for install_repo

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
update the docs on the new install subcommand

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>

Closes #222
Merge pull request #220 from thesues/master

check if bootstrap-osd exsits before creating the keyring file