fix some warnings from shellcheck

Signed-off-by: Mattia Rizzolo <mapreri@ubuntu.com>

deploy

@@ -8,7 +8,7 @@ DIR_ENVIRONMENTS="envs"
 DIR_ROLES="roles"
 DIR_GROUP_VARS="group_vars"
 
-FILE_VAULT_PASSWORD="vault-password"
+#FILE_VAULT_PASSWORD="vault-password"
 
 BIN_ANSIBLE_PLAYBOOK="ansible-playbook"
 
@@ -40,7 +40,7 @@ if [[ ! -d "${env}" ]]; then
     echo
 
     echo "available environments:"
-    for available in `ls -1 "${DIR_ENVIRONMENTS}"`; do
+    for available in $(ls -1 "${DIR_ENVIRONMENTS}"); do
         echo " - ${available}"
     done
     exit 1
@@ -50,8 +50,8 @@ if [[ ! -f "${playbook_file}" ]]; then
     echo
 
     echo "available playbooks:"
-    for available in `ls -1 "${DIR_PLAYBOOKS}"`; do
-        echo " - `echo "${available}" | sed 's/\.yml$//'`"
+    for available in $(ls -1 "${DIR_PLAYBOOKS}"); do
+        echo " - ${available%.yml}"
     done
     exit 1
 fi
@@ -62,13 +62,13 @@ function cleanup () { rm -rf "$DIR_TEMP"; }
 mkdir -p "$DIR_TEMP/play"
 trap cleanup EXIT
 
-ln -s "`readlink -e "${DIR_ROLES}"`" "${DIR_TEMP}/play/roles"
-ln -s "`readlink -e "${DIR_GROUP_VARS}"`" "${DIR_TEMP}/play/group_vars"
-ln -s "`readlink -e "${playbook_file}"`" "${DIR_TEMP}/play/playbook.yml"
-ln -s "`readlink -e "${env}"`" "${DIR_TEMP}/env"
+ln -s "$(readlink -e "${DIR_ROLES}")" "${DIR_TEMP}/play/roles"
+ln -s "$(readlink -e "${DIR_GROUP_VARS}")" "${DIR_TEMP}/play/group_vars"
+ln -s "$(readlink -e "${playbook_file}")" "${DIR_TEMP}/play/playbook.yml"
+ln -s "$(readlink -e "${env}")" "${DIR_TEMP}/env"
 
 # Finally execute the playbook against the server
 "${BIN_ANSIBLE_PLAYBOOK}" -i "${DIR_TEMP}/env/hosts" \
                          "${DIR_TEMP}/play/playbook.yml" \
                          -vv --diff \
-                         $@
+                         "${@}"