Delay import of psutil to avoid AVC

Commit cfad7af35d added a check to ensure a
system has sufficient amount of memory. The feature uses psutil to get
available memory. On import psutil opens files in /proc which can result in
an SELinux violations and Python exception.

     PermissionError: [Errno 13] Permission denied: '/proc/stat'

Fixes: https://pagure.io/freeipa/issue/8512
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipaserver/install/installutils.py

@@ -29,7 +29,6 @@ import ldif
 import os
 import re
 import fileinput
-import psutil
 import sys
 import tempfile
 import shutil
@@ -1035,6 +1034,9 @@ def check_available_memory(ca=False):
                 "Unable to determine the amount of available RAM"
             )
     else:
+        # delay import of psutil. On import it opens files in /proc and
+        # can trigger a SELinux violation.
+        import psutil
         available = psutil.virtual_memory().available
     logger.debug("Available memory is %sB", available)
     if available < minimum_suggested: