Use Dogtag 10 only when it is available

Put the changes from Ade's dogtag 10 patch into namespaced constants in
dogtag.py, which are then referenced in the code.

Make ipaserver.install.CAInstance use the service name specified in the
configuration. Uninstallation, where config is removed before CA uninstall,
also uses the (previously) configured value.

This and Ade's patch address https://fedorahosted.org/freeipa/ticket/2846

install/tools/ipa-replica-install

@@ -42,6 +42,7 @@ from ipapython.config import IPAOptionParser
 from ipapython import sysrestore
 from ipapython import services as ipaservices
 from ipapython.ipa_log_manager import *
+from ipapython import dogtag
 from ipapython.dn import DN
 
 log_file_name = "/var/log/ipareplica-install.log"
@@ -376,7 +377,8 @@ def main():
         if ipautil.file_exists(config.dir + "/cacert.p12"):
             fd.write("enable_ra=True\n")
             fd.write("ra_plugin=dogtag\n")
-            fd.write("dogtag_version=10\n")
+            fd.write("dogtag_version=%s\n" %
+                dogtag.install_constants.DOGTAG_VERSION)
         fd.write("mode=production\n")
         fd.close()
     finally: