[ashell] Ctrl+X still saves input through load command

[qiaojingx]

Description

Content inputted through load command isn't abandoned when exiting by CTRL+X

Test Code

Ashell;

Steps to Reproduction

1. make ashell ROM=256
2. make dfu
3. acm> load test.js
4. RAW>/*input something*/
5. CTRL+X to exit

Actual Result

Expected Result

Content inputted should not be saved.

Test Builds

Branch	Commit Id	Target Device	Test Date	Result
master	82662d6	Arduino 101	Apr. 19, 2018	Fail

Additional Information

Open a separate issue since it is still reproduced in ashell and #1446 has been closed for this feature has been abandoned in IDE.