cli: ovirt-shell does not exit when using -f option(#854519)

ovirt-shell does not exit when -f option is used. This option
is used by system scripts and it would be useful to exit the
ovirt-shell upon completion of the command execution.

Change-Id: I5441a401ed39fc7148b6001fb826b145ba66d6c7
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=854519
Signed-off-by: Ravi Nori <rnori@redhat.com>