Make --setup-dns work on replica installation

The ipa-replica-install script will setup the DNS if user specifies the
--setup-dns option. It will only add the zone into LDAP if the
cn=dns,$SUFFIX container doesn't exist. For now, however, we do not add
the records.

install/tools/man/ipa-replica-install.1

@@ -35,6 +35,9 @@ Do not configure NTP
 .TP 
 \fB\-p\fR, \fB\-\-password\fR=\fIDM_PASSWORD\fR 
 Directory Manager (existing master) password
+.TP
+\fB\-\-setup\-dns\fR
+Generate a DNS zone if it does not exist already and configure the DNS server
 .SH "EXIT STATUS"
 0 if the command was successful