pam UPDATE auth using Linux PAM

Added the ability to authenticate via Linux PAM when using keyboard-interactive SSH authentication method. One new API call was added.
diff --git a/tests/client/test_client_ssh.c b/tests/client/test_client_ssh.c
index b298795..2cab032 100644
--- a/tests/client/test_client_ssh.c
+++ b/tests/client/test_client_ssh.c
@@ -447,11 +447,11 @@
 
     /* check default prefference settings according to documentation */
     ret = nc_client_ssh_get_auth_pref(NC_SSH_AUTH_INTERACTIVE);
-    assert_int_equal(ret, 3);
+    assert_int_equal(ret, 1);
     ret = nc_client_ssh_get_auth_pref(NC_SSH_AUTH_PASSWORD);
     assert_int_equal(ret, 2);
     ret = nc_client_ssh_get_auth_pref(NC_SSH_AUTH_PUBLICKEY);
-    assert_int_equal(ret, 1);
+    assert_int_equal(ret, 3);
 
     /* try to set prefetence of non existing method */
     nc_client_ssh_set_auth_pref(42, 22);