Use a SSH pool to manage SSH connection

Use a SSH pool to hold all SSH clients.It allows 4 SSH clients
at most to connect to the SSH server at the same time.
This patchset also enables every SSH client connect to the other
controller when they failed to connect to the current controller.
For example,failed to A,then to B,or,failed to B,then to A.

Fixes bug: 1162251
Change-Id: I86f7f684639034be97ddf2031e61ac6bf3a196ad
NetApp: Fix failing NetApp tests

The tests were failing due to an upgrade in the testing framework
(possibly due to upgrade of nose package from 1.2.1 to 1.3.0).
The actual reason was a bug in the suds client. A simple
workaround is utilised here, which sets the logging level of a
suds file to INFO instead of DEBUG.

Some 'FutureWarning' warnings from the test output were also
fixed.

Change-Id: Ia67476c23bffa91264cf79f6a26944b450c4f4fc
Merge "Use a SSH pool to manage SSH connection"
Merge "NetApp: Fix failing NetApp tests"