cli: implement CLI invocation capabilities #895559

implemented by -E/--execute-command option, e.g:

[mpastern@laptop ~]$ ovirt-shell --execute-command "list vms;list clusters"

[oVirt shell (connected)]# list vms

id         : 77fd5b88-bcd6-4296-bf20-f3d857f7f0d2
name       : test

[oVirt shell (connected)]# list clusters

id         : 99408929-82cf-4dc7-a532-9d998063fa95
name       : Default
description: The default server cluster

[mpastern@laptop ~]$
[mpastern@laptop ~]$
[mpastern@laptop ~]$

Change-Id: Ie1d31b3321441b7efef6a27f6223ef96c803f1e5
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=895559
Signed-off-by: Michael pasternak <mpastern@redhat.com>