Travis: install gnutls-bin for all jobs

Some jobs don't actually test against GnuTLS, but all.sh checks its
presence in all test jobs, so it needs to be installed regardless.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/.travis.yml b/.travis.yml
index c3580b8..c3bd352 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@
       addons:
         apt:
           packages:
+          - gnutls-bin
           - doxygen
           - graphviz
       language: python # Needed to get pip for Python 3
@@ -20,10 +21,6 @@
         - tests/scripts/all.sh -k test_default_out_of_box
 
     - name: full configuration
-      addons:
-        apt:
-          packages:
-          - gnutls-bin
       script:
         - tests/scripts/all.sh -k test_full_cmake_gcc_asan
 
@@ -42,6 +39,9 @@
     - secure: "FrI5d2s+ckckC17T66c8jm2jV6i2DkBPU5nyWzwbedjmEBeocREfQLd/x8yKpPzLDz7ghOvr+/GQvsPPn0dVkGlNzm3Q+hGHc/ujnASuUtGrcuMM+0ALnJ3k4rFr9xEvjJeWb4SmhJO5UCAZYvTItW4k7+bj9L+R6lt3TzQbXzg="
 
 addons:
+  apt:
+    packages:
+    - gnutls-bin
   coverity_scan:
     project:
       name: "ARMmbed/mbedtls"