Make ironic ssh check timeout configurable

On some environments, the current 10s timeout waiting for server
ssh-able is not enough. SSH session was killed before the command
executed by server and then break the whole stack.sh.

Change-Id: I4d842744793455d44a633dee8920a60552e8075e
diff --git a/lib/ironic b/lib/ironic
index 35b5411..863d023 100644
--- a/lib/ironic
+++ b/lib/ironic
@@ -63,6 +63,7 @@
 IRONIC_BAREMETAL_BASIC_OPS=$(trueorfalse False IRONIC_BAREMETAL_BASIC_OPS)
 IRONIC_ENABLED_DRIVERS=${IRONIC_ENABLED_DRIVERS:-fake,pxe_ssh,pxe_ipmitool}
 IRONIC_SSH_USERNAME=${IRONIC_SSH_USERNAME:-`whoami`}
+IRONIC_SSH_TIMEOUT=${IRONIC_SSH_TIMEOUT:-15}
 IRONIC_SSH_KEY_DIR=${IRONIC_SSH_KEY_DIR:-$IRONIC_DATA_DIR/ssh_keys}
 IRONIC_SSH_KEY_FILENAME=${IRONIC_SSH_KEY_FILENAME:-ironic_key}
 IRONIC_KEY_FILE=${IRONIC_KEY_FILE:-$IRONIC_SSH_KEY_DIR/$IRONIC_SSH_KEY_FILENAME}
@@ -703,7 +704,7 @@
 
 function configure_ironic_auxiliary {
     configure_ironic_ssh_keypair
-    ironic_ssh_check $IRONIC_KEY_FILE $IRONIC_VM_SSH_ADDRESS $IRONIC_VM_SSH_PORT $IRONIC_SSH_USERNAME 10
+    ironic_ssh_check $IRONIC_KEY_FILE $IRONIC_VM_SSH_ADDRESS $IRONIC_VM_SSH_PORT $IRONIC_SSH_USERNAME $IRONIC_SSH_TIMEOUT
 }
 
 function build_ipa_coreos_ramdisk {