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/cinder_plugins/solidfire b/lib/cinder_plugins/solidfire
index 47c113e..2c970b5 100644
--- a/lib/cinder_plugins/solidfire
+++ b/lib/cinder_plugins/solidfire
@@ -27,7 +27,7 @@
 # ------------
 
 # configure_cinder_driver - Set config files, create data dirs, etc
-function configure_cinder_driver() {
+function configure_cinder_driver {
     # To use solidfire, set the following in localrc:
     # CINDER_DRIVER=solidfire
     # SAN_IP=<mvip>