Create utils method for checking guest cmd output in the integration tests

[serban300]

In the integration tests there are multiple functions that execute a command on the guest and then compare the output with some expected values. Like this one

Create one utils method that does this and call it when needed instead of having a couple of similar methods scattered throughout the integration tests.

See the comment here

[andreeaflorescu]

@serban300 your link goes to "We went looking everywhere, but couldn’t find those commits.". Please add a proper description for this issue.

[dhriti-rajan]

Hello! My name's Dhriti, I'm currently taking the CS 360V Virtualization course at UT Austin. One of our projects for the class is to work on an issue in an open-source repository, and this repository looked pretty cool. Would it be alright if I worked on this issue?