ssh: avoid connection timeouts

On some hypervistor the sosreport collection can take
more than 900 seconds (default ClientAliveInterval).
Calling ssh with -oServerAliveInterval=600 avoid the
connection timeout for ServerAliveCountMax (deafults=3)
times.

Change-Id: I19075dd1a39ed0f9f7242897157d017c2375aad6
Bug-Url: https://bugzilla.redhat.com/962677
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>