specify full path for exportfs

The autocleaner.py is executed by cron which sets path to
PATH=/usr/bin:/bin. As exportfs is in /usr/sbin it must have full path
specified, otherwise the script is crashing and fails to clean up old
jobs directories

Fixes freeipa#422

autocleaner.py

@@ -149,7 +149,7 @@ def prune_exports_file(prune_dirs):
     exports.close()
 
     # sync exportfs before deleting the folders
-    subprocess.run(['exportfs', '-ar'], timeout=TIMEOUT)
+    subprocess.run(['/usr/sbin/exportfs', '-ar'], timeout=TIMEOUT)
 
     return entries_deleted