Warn about potential loss of CA, KRA, DNSSEC during uninstall

If connection do LDAP failed (or LDAP server is down) we cannot verify
if there is any additonal instance of CA, KRA, DNSSEC master.
In this case a user is warned and promted to confirm uninstallation.

https://fedorahosted.org/freeipa/ticket/5544

Reviewed-By: David Kupka <dkupka@redhat.com>

ipaserver/install/server/install.py

@@ -1078,8 +1078,18 @@ def uninstall_check(installer):
         msg = ("\nWARNING: Failed to connect to Directory Server to find "
                "information about replication agreements. Uninstallation "
                "will continue despite the possible existing replication "
-               "agreements.\n\n")
+               "agreements.\n\n"
+               "If this server is the last instance of CA, KRA, or DNSSEC "
+               "master, uninstallation may result in data loss.\n\n"
+        )
         print(textwrap.fill(msg, width=80, replace_whitespace=False))
+
+        if (installer.interactive and not user_input(
+                "Are you sure you want to continue with the uninstall "
+                "procedure?", False)):
+            print("")
+            print("Aborting uninstall operation.")
+            sys.exit(1)
     else:
         dns.uninstall_check(options)