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/tools/jenkins/build_configuration.sh b/tools/jenkins/build_configuration.sh
index e295ef2..64ee159 100755
--- a/tools/jenkins/build_configuration.sh
+++ b/tools/jenkins/build_configuration.sh
@@ -5,7 +5,7 @@
 ADAPTER=$3
 RC=$4
 
-function usage() {
+function usage {
     echo "Usage: $0 -  Build a configuration"
     echo ""
     echo "$0 [EXECUTOR_NUMBER] [CONFIGURATION] [ADAPTER] [RC (optional)]"
diff --git a/tools/jenkins/configurations/kvm.sh b/tools/jenkins/configurations/kvm.sh
index d9a160a..6927fd7 100755
--- a/tools/jenkins/configurations/kvm.sh
+++ b/tools/jenkins/configurations/kvm.sh
@@ -9,7 +9,7 @@
 ADAPTER=$3
 RC=$4
 
-function usage() {
+function usage {
     echo "Usage: $0 - Build a test configuration"
     echo ""
     echo "$0 [EXECUTOR_NUMBER] [CONFIGURATION] [ADAPTER] [RC (optional)]"
diff --git a/tools/jenkins/configurations/xs.sh b/tools/jenkins/configurations/xs.sh
index 864f949..7b671e9 100755
--- a/tools/jenkins/configurations/xs.sh
+++ b/tools/jenkins/configurations/xs.sh
@@ -8,7 +8,7 @@
 ADAPTER=$3
 RC=$4
 
-function usage() {
+function usage {
     echo "Usage: $0 - Build a test configuration"
     echo ""
     echo "$0 [EXECUTOR_NUMBER] [CONFIGURATION] [ADAPTER] [RC (optional)]"
diff --git a/tools/jenkins/run_test.sh b/tools/jenkins/run_test.sh
index 4649563..d2b8284 100755
--- a/tools/jenkins/run_test.sh
+++ b/tools/jenkins/run_test.sh
@@ -4,7 +4,7 @@
 ADAPTER=$2
 RC=$3
 
-function usage() {
+function usage {
     echo "Usage: $0 - Run a test"
     echo ""
     echo "$0 [EXECUTOR_NUMBER] [ADAPTER] [RC (optional)]"