Enforce function declaration format in bash8

Check that function calls look like ^function foo {$ in bash8, and fix
all existing failures of that check.  Add a note to HACKING.rst

Change-Id: Ic19eecb39e0b20273d1bcd551a42fe400d54e938
diff --git a/lib/neutron_thirdparty/midonet b/lib/neutron_thirdparty/midonet
index 98be425..ad417bb 100644
--- a/lib/neutron_thirdparty/midonet
+++ b/lib/neutron_thirdparty/midonet
@@ -20,28 +20,28 @@
 MY_XTRACE=$(set +o | grep xtrace)
 set +o xtrace
 
-function configure_midonet() {
+function configure_midonet {
     :
 }
 
-function init_midonet() {
+function init_midonet {
     :
 }
 
-function install_midonet() {
+function install_midonet {
     git_clone $MIDONET_CLIENT_REPO $MIDONET_CLIENT_DIR $MIDONET_CLIENT_BRANCH
     export PYTHONPATH=$MIDONET_CLIENT_DIR/src:$PYTHONPATH
 }
 
-function start_midonet() {
+function start_midonet {
     :
 }
 
-function stop_midonet() {
+function stop_midonet {
     :
 }
 
-function check_midonet() {
+function check_midonet {
     :
 }