The previously default /home/stack/.ssh/id_rsa.pub file may not exist or
be readable; exit with explicit error message. Users can still specify a
file path but will need to ensure it is readable. Should a file path not
be specified, default to amp_ssh_key_data. The value is passed by THT
with the public key of the 'default' keypair from the undercloud which
anyway is the public key of the 'stack' user.
This patch also fixes a syntax error in octavia-undercloud role.
Closes-Bug: #1770153
Closes-Bug: #1770641
Depends-On: https://review.openstack.org/568022
Change-Id: I0026343d90b84572c3002fa21001cfb09c742391
8a69b692c4