Fix sudo account password error message

Recent changes to the Clear Linux base image cause the final line
in the setup.py script to yield an error message and exit.

There are numerous ways this could be fixed, but this fix (suggested
by @shrmrf) is the minimal change needed.

Signed-off-by: Kevin C. Wells <kevin.c.wells@intel.com>

clr-sdk/setup.py

@@ -75,6 +75,6 @@ except FileExistsError:
 
 # Move to mixdir and start bash as new user
 os.chdir(mixdir)
-cmd = "sudo -H -u {} bash -i".format(user).split()
+cmd = "su {}".format(user).split()
 os.execvp(cmd[0], cmd)