[Console] Fix side-effects from running bash completions

Author: Seldaek

src/Symfony/Component/Console/Resources/completion.bash

@@ -7,7 +7,7 @@
 
 _sf_{{ COMMAND_NAME }}() {
     # Use newline as only separator to allow space in completion values
-    IFS=$'\n'
+    local IFS=$'\n'
     local sf_cmd="${COMP_WORDS[0]}"
 
     # for an alias, get the real script behind it