ssh: Prefer algorithms of the known host keys

ssh: Prefer algorithms of the known host keys

JSch prefers ssh-rsa key type. When the remote server supports ssh-rsa
key type then this key type will be used even if the known_hosts file
contains a host key for that host, but with different key type.
This caused an unexpected UnknownHostKey error.

To fix the issue first scan the known_hosts, the HostKeyRepository in
JSch API, for any already existing host keys for the target host and
modify the default session settings to prefer their algorithms. However,
do this only if there is no HostKeyAlgorithms setting active.

Change-Id: I236df2a860ddd9289a0a820ddf09c2dea3673d36