Fix known_hosts.py to work on older versions of python

lib/ansible/module_utils/known_hosts.py

@@ -27,7 +27,12 @@
 # USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import hmac
+
+try:
     from hashlib import sha1
+except ImportError:
+    import sha as sha1
+
 HASHED_KEY_MAGIC = "|1|"
 
 def add_git_host_key(module, url, accept_hostkey=True, create_dir=True):