API: host-deploy: Adding ssh username, port and fingerprint to host information

Those additional fields are used to authenticate with the host during
deploy process. Currently we use default port (22) and root user to
connect to host. This patch adds the capability to use configurable
port and specific user values, and avoiding using root password to install or
update new host.

<host>
 ...
 <ssh>
  <port>22</port>
  <fingerprint>aa:bb:cc:dd:ee:ff:aa:bb</fingerprint>
  <authentication_method>PublicKey</authentication_mathod>
  <user>
   <password></password>
   ...
  </user>
 </ssh>
 ...
</host>

Change-Id: Ic18e91f1602af42e7c73acea5d875c54545cb3c2
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>