FIX: VAT SSH timeout

FIX: VAT SSH timeout

Currently when VAT cannot connect to VPP via direct API call, there is
inner timeout of ~100s until it quits and returns RC. In our code we are
setting outer timeout to 10/15s to detect if VAT is not responding. If
VAT does not respond quickly enough due to e.g VPP crash, we are
incorrectly reporting SSHTimout exception.

This fix is suppose to set correct timeout values and also to set some
of the calls like show run|hard|err / clear to detect whether they were
successfull or not.

+ Various small library cleanup.

Change-Id: I787c4baecd7e086705a4076643e255a875ea8438
Signed-off-by: Peter Mikus <pmikus@cisco.com>
(cherry picked from commit 84e2999a1b8847e4ae43cc2b0faf901ac8575bc1)