Change tests in shell scripts to be more compatible with Bourne shell

This is needed for the scripts to work in Alpine Linux, which
comes with a Bourne shell.

Author: flaix

src/main/distrib/linux/migrate-tickets.sh

@@ -8,7 +8,7 @@
 #
 # --------------------------------------------------------------------------
 
-if [[ -z $1 || -z $2 ]]; then
+if [ -z $1 ] || [ -z $2 ]; then
     echo "Please specify the output ticket service and your baseFolder!";
     echo "";
     echo "usage:";

src/main/distrib/linux/reindex-tickets.sh

@@ -11,7 +11,7 @@
 #
 # --------------------------------------------------------------------------
 
-if [[ -z $1 ]]; then
+if [ -z $1 ] ; then
     echo "Please specify your baseFolder!";
     echo "";
     echo "usage:";