MB-11167: choose whatever pysnappy module that works

On some centos platforms, it is possible tha there are more than
one python installed and it is totally based on PATH value to decide
which python to use. As result, we should either way and find the
verstion that works

Change-Id: If826c90e5addbd20e0028c7ae537b047d0712661
Reviewed-on: http://review.couchbase.org/37533
Reviewed-by: Bin Cui <bin.cui@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>