pylint: fix simplifiable-if-statement warnings

fix inefficient if statements, enable pylint check

Reviewed-By: Tomas Krizek <tkrizek@redhat.com>
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>

ipaserver/install/ca.py

@@ -126,15 +126,10 @@ def install_step_0(standalone, replica_config, options):
 
     if replica_config is not None:
         # Configure the CA if necessary
-        if standalone:
-            postinstall = True
-        else:
-            postinstall = False
-
         if standalone:
             api.Backend.ldap2.disconnect()
 
-        cainstance.install_replica_ca(replica_config, postinstall,
+        cainstance.install_replica_ca(replica_config, standalone,
                 ra_p12=getattr(options, 'ra_p12', None))
 
         if standalone and not api.Backend.ldap2.isconnected():