qa/cephfs: remove sudo parameter from run_shell()

qa/cephfs: remove sudo parameter from run_shell()

Right now, run_shell() in mount.py accepts both "sudo" and "omit_sudo"
as parameters. It's better to accept only one of these two parameters.
A call to run_shell() where both are set to opposing values will be
buggy. Therefore, methods calling run_shell() must add "sudo" to command
arguments before call and set omit_sudo to False in call.

As a result of this change, methods like stat() and run_python() in
mount.py are now modified to add "sudo" to command arguments
and set omit_sudo to False within their own definitions.

Signed-off-by: Rishabh Dave <ridave@redhat.com>