Fix stuff from tests

ShellCheck tests have brought up a couple of issues, that I was not aware of needed to be taken care. This should fix the tests.

dnsapi/dns_pleskxml.sh

@@ -386,7 +386,7 @@ _pleskxml_get_root_domain() {
   # We don't actually need to check for type, name, *and* id, but it guarantees only usable lines are returned.
 
   output="$(_api_response_split "$pleskxml_prettyprint_result" 'result' '<status>ok</status>' | sed 's/<ascii-name>/<name>/g;s/<\/ascii-name>/<\/name>/g' | grep '<name>' | grep '<id>')"
-  debug_output="$(printf "$output" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
+  debug_output="$(printf "%s" "$output" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
 
   _debug 'Domains managed by Plesk server are:'
   _debug "$debug_output"
@@ -405,15 +405,15 @@ _pleskxml_get_root_domain() {
   # We don't actually need to check for type, name, *and* id, but it guarantees only usable lines are returned.
 
   output_additional="$(_api_response_split "$pleskxml_prettyprint_result" 'result' '<status>ok</status>' | sed 's/<ascii-name>/<name>/g;s/<\/ascii-name>/<\/name>/g' | grep '<name>' | grep '<id>')"
-  debug_additional="$(printf "$output_additional" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
+  debug_additional="$(printf "%s" "$output_additional" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
 
   _debug 'Additional domains managed by Plesk server are:'
   _debug "$debug_additional"
 
   # Concate the two outputs together.
 
-  output="$(printf "$output $NEWLINE $output_additional")"
-  debug_output="$(printf "$output" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
+  output="$(printf "%s" "$output $NEWLINE $output_additional")"
+  debug_output="$(printf "%s" "$output" | sed -n 's:.*<name>\(.*\)</name>.*:\1:p')"
 
   _debug 'Domains (including additional) managed by Plesk server are:'
   _debug "$debug_output"