Webcamshutdown - use FUNC_ABOUT_TO_RESTART

[btsimonh]

Description:

WebcamV2 would die if FUNC_SAVE_BEFORE_RESTART was called, so replace with the new FUNC_ABOUT_TO_RESTART.
Also resolve a small compile warning...

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.6
• The code change is tested and works with Tasmota core ESP32 V.3.0.0
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass