(NEXMANAGE-1281) Return error message when restart and shutdown fail on not able to fi…

[nmgaston]

…nd file

PULL DESCRIPTION

Returns the correct error when the /sbin/shutdown file is not found. Needed to catch the FileNotFound exception.

Impact Analysis

Info	Please fill out this column
Root Cause	Dispatcher Device Manager needed to catch the FileNotFound exception when performing a shutdown or restart
Jira ticket	NEXMANAGE-1281

CODE MAINTAINABILITY

• Added required new tests relevant to the changes
• Updated Documentation as relevant to the changes
• PR change contains code related to security
• PR introduces changes that break compatibility with other modules/services (If YES, please provide description)
• Run go fmt or format-python.sh as applicable
• Update Changelog
• Integration tests are passing
• If Cloudadapter changes, check Azure connectivity manually

Code must act as a teacher for future developers