compat: Save server's API version in for pre-schema servers

When client comunicates with server that doesn't support 'schema'
command it needs to determine its api version to be able to use the
right compat code. Storing information about server version reduces the
need to call 'env' or 'ping' command only to first time the server is
contacted.

https://fedorahosted.org/freeipa/ticket/6069

Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaplatform/base/paths.py

@@ -21,6 +21,8 @@
 This base platform module exports default filesystem paths.
 '''
 
+import os
+
 
 class BasePathNamespace(object):
     BASH = "/bin/bash"
@@ -353,4 +355,17 @@ class BasePathNamespace(object):
     IPA_CUSTODIA_AUDIT_LOG = '/var/log/ipa-custodia.audit.log'
     IPA_GETKEYTAB = '/usr/sbin/ipa-getkeytab'
 
+    @property
+    def USER_CACHE_PATH(self):
+        return (
+            os.environ.get('XDG_CACHE_HOME') or
+            os.path.join(
+                os.environ.get(
+                    'HOME',
+                    os.path.expanduser('~')
+                ),
+                '.cache'
+            )
+        )
+
 path_namespace = BasePathNamespace