Changes

pySim-shell_test/utils: treat cmd2 error "not a recognized command... as exception

When a pySim-shell command is not recognized, cmd2 prints "xyz is not a
recognized command, alias, or macro." This string is a normal print out
and not an exception, but during tests, it may point out a severe problem
and therefore it should be tread like an exception.

Related: OS#6367
Change-Id: I17be6af1547b31170622e17b9cfb9c492597670d