package/openssh: also install ssh-copy-id script

package/openssh: also install ssh-copy-id script

This script is useful to copy SSH keys between client and server [1] and
installed on most distributions (for example on debian: [2]).

[1] https://www.ssh.com/ssh/copy-id
[2] https://packages.debian.org/fr/jessie/armhf/openssh-client/filelist

Signed-off-by: Julien BOIBESSOT <julien.boibessot@armadeus.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[Thomas: use full destination path.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>