Add RSA sig+enc test to travis

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/.travis.yml b/.travis.yml
index 813e0b7..225641e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,6 +25,8 @@
       env: MULTI_FEATURES="sig-rsa validate-slot0,sig-ecdsa validate-slot0"
     - os: linux
       env: MULTI_FEATURES="enc-kw overwrite-only,enc-rsa overwrite-only"
+    - os: linux
+      env: MULTI_FEATURES="sig-rsa enc-rsa validate-slot0"
 
     # FIXME: this test actually fails and must be fixed
     #- os: linux