nuageinit: fix shell injection in power_state_change delay and add test

libexec/nuageinit/nuageinit

@@ -748,7 +748,7 @@ local function power_state_change(obj)
 	end
 
 	-- Build shutdown command
-	local cmd = "shutdown -" .. flag .. " " .. delay
+	local cmd = "shutdown -" .. flag .. " " .. nuage.shell_escape(delay)
 	if message then
 		cmd = cmd .. " " .. nuage.shell_escape(message)
 	end

libexec/nuageinit/tests/nuageinit.sh

@@ -1332,7 +1332,7 @@ power_state:
   timeout: 30
   condition: true
 EOF
-	atf_check -o inline:"shutdown -r +5 'Rebooting after configuration is complete'\n" \
+	atf_check -o inline:"shutdown -r '+5' 'Rebooting after configuration is complete'\n" \
 	    /usr/libexec/nuageinit "${PWD}"/media/nuageinit postnet
 	true
 }