Reformat shell scripts with shfmt

All changes in this commit were automated using the command:

  shfmt -w -i 2 -ci -bn . $(find . -name "*.sh.in")

By default, only *.sh and files without extension are checked, so
*.sh.in files have to be added additionally. (See mvdan/sh#944)

bin/tests/system/upforwd/prereq.sh

@@ -13,10 +13,9 @@
 
 . ../conf.sh
 
-if ! ${PERL} -MNet::DNS -e ''
-then
-	echo_i "perl Net::DNS module is required"
-	exit 1
+if ! ${PERL} -MNet::DNS -e ''; then
+  echo_i "perl Net::DNS module is required"
+  exit 1
 fi
 
 exit 0