Add passphrase generation for Octavia

A recent change[1] to Octavia added a parameter named
server_certs_key_passphrase, which means that we should generate a
password for it to avoid using the default value.

This patch adds OctaviaServerCertsKeyPassphrase to the list of
generated password/secrets, similarly to this past change[2].

Closes-Bug: #1821756
Related-Bug: #1821751

[1] I06d329ca53bc36bd27f7870ae7c7ca0cf18575b2
[2] I1dd1873b646e8569ed0a85c5ee7eb3bec3a8b1fa

Change-Id: I9699961faf8b3430e4372e4ff3ae2bf7e7ceea18

tripleo_common/constants.py

@@ -115,6 +115,7 @@ PASSWORD_PARAMETER_NAMES = (
     'NovaPassword',
     'NovajoinPassword',
     'MigrationSshKey',
+    'OctaviaServerCertsKeyPassphrase',
     'OctaviaCaKeyPassphrase',
     'OctaviaHeartbeatKey',
     'OctaviaPassword',

tripleo_common/tests/actions/test_parameters.py

@@ -60,6 +60,7 @@ _EXISTING_PASSWORDS = {
     'PankoPassword': 'cVZXehsSc2KdmFFMKDudxTLKn',
     'OctaviaHeartbeatKey': 'oct-heartbeat-key',
     'OctaviaPassword': 'NMl7j3nKk1VVwMxUZC8Cgw==',
+    'OctaviaServerCertsKeyPassphrase': 'aW5zZWN1cmUta2V5LWRvLW5vdC11c2U=',
     'OctaviaCaKeyPassphrase': 'SLj4c3uCk4DDxPwQOG1Heb==',
     'ManilaPassword': 'NYJN86Fua3X8AVFWmMhQa2zTH',
     'NeutronMetadataProxySharedSecret': 'Q2YgUCwmBkYdqsdhhCF4hbghu',