FIX: SSH socket reading error

Currently if the command timeouts due to the nature of script execution
we are trying to again read from socket after timeout on seesion
expired. This patch is supposed to fix the behaviour and eliminate the
second read from channel after it was cloed.

Change-Id: Ib0028e901eb6ff4d10ca77d2ea19f9e770e6cef4
Signed-off-by: Peter Mikus <pmikus@cisco.com>