a-o-i: Redo logic for detecting master_lb

After much research and debugging, it turns out the facts
for nativeha hosts were much less consistent than I hoped.
With this newfound knowledge, I've implemented this method.

In short, you check with the first master to see what it thinks
the master_lb is, then you include that host as "installed".

utils/src/ooinstall/cli_installer.py

@@ -528,18 +528,27 @@ Add new nodes here
 
 def get_installed_hosts(hosts, callback_facts):
     installed_hosts = []
+
+    # count nativeha lb as an installed host
+    try:
+        first_master = next(host for host in hosts if host.master)
+        lb_hostname = callback_facts[first_master.connect_to]['master'].get('cluster_hostname', '')
+        lb_host = next(host for host in hosts if host.connect_to == lb_hostname)
+        installed_hosts.append(lb_host)
+    except KeyError:
+        pass
+
+
     for host in hosts:
-        if host.connect_to in callback_facts.keys() and (
-            ('common' in callback_facts[host.connect_to].keys() and
-                  callback_facts[host.connect_to]['common'].get('version', '') and
-                  callback_facts[host.connect_to]['common'].get('version', '') != 'None') \
-            or
-            ('master' in callback_facts[host.connect_to].keys() and
-                 callback_facts[host.connect_to]['master'].get('cluster_hostname', '') == host.connect_to)
-            ):
+        if host.connect_to in callback_facts.keys() and is_installed_host(host, callback_facts):
             installed_hosts.append(host)
     return installed_hosts
 
+def is_installed_host(host, callback_facts):
+    return 'common' in callback_facts[host.connect_to].keys() and \
+           callback_facts[host.connect_to]['common'].get('version', '') and \
+           callback_facts[host.connect_to]['common'].get('version', '') != 'None'
+
 # pylint: disable=too-many-branches
 # This pylint error will be corrected shortly in separate PR.
 def get_hosts_to_run_on(oo_cfg, callback_facts, unattended, force, verbose):