Configure ironic to use Ipmitool retries

Without this configuration, the ipmitool timeout is 1 second. This is too short
for vbmc. This commit uses the ipmitool retry feature and extends the timeout

ironic.conf

@@ -64,3 +64,20 @@ uefi_pxe_config_template = $pybasedir/drivers/modules/ipxe_config.template
 
 [redfish]
 use_swift = false
+
+[ipmi]
+# use_ipmitool_retries transfers the responsibility of retrying to ipmitool
+# when supported. If set to false, then ipmitool is called as follows :
+#    $ipmitool -R 1 -N 1 ...
+# and Ironic handles the retry loop.
+use_ipmitool_retries = true
+# The following parameters are the defaults in Ironic. They are used in the
+# following way if use_ipmitool_retries is set to true:
+#    $ipmitool -R <X> -N <Y> ...
+# where :
+#    X = command_retry_timeout / min_command_interval
+#    Y = min_command_interval
+# If use_ipmitool_retries is false, then ironic retries X times, with an
+# interval of Y in between each tries.
+min_command_interval = 5
+command_retry_timeout = 60