Improve dnsrecord-add interactive mode

When an invalid record type is entered during dnsrecord-add
interactive mode, user is provided with a list of allowed values
(record types). However, the provided list contains also
unsupported record types (APL, DHCID, etc.) and any attempt to add
such records would end with error. This patch limits the list
to supported record types only.

https://fedorahosted.org/freeipa/ticket/2378

ipalib/plugins/dns.py

@@ -1376,6 +1376,8 @@ def __dns_record_options_iter():
             yield extra
 
 _dns_record_options = tuple(__dns_record_options_iter())
+_dns_supported_record_types = tuple(record.rrtype for record in _dns_records \
+                                    if record.supported)
 
 # dictionary of valid reverse zone -> number of address components
 _valid_reverse_zones = {
@@ -1938,9 +1940,12 @@ class dnsrecord_add(LDAPCreate):
 
                 if not isinstance(param, DNSRecord):
                     raise ValueError()
-            except KeyError, ValueError:
+
-                all_types = u', '.join(_record_types)
+                if not param.supported:
-                self.Backend.textui.print_plain(_(u'Invalid type. Allowed values are: %s') % all_types)
+                    raise ValueError()
+            except (KeyError, ValueError):
+                all_types = u', '.join(_dns_supported_record_types)
+                self.Backend.textui.print_plain(_(u'Invalid or unsupported type. Allowed values are: %s') % all_types)
                 continue
             ok = True
 
@@ -1964,7 +1969,7 @@ class dnsrecord_add(LDAPCreate):
                 # check if any record part was added
                 try:
                     rrparam = self.params[param.hint]
-                except KeyError, AttributeError:
+                except (KeyError, AttributeError):
                     continue
 
                 if rrparam.name in entry_attrs: