travis.yml: Build and start the simulator before we run 'make check'.

This is required by the integration tests.

Signed-off-by: Philip Tricca <philip.b.tricca@intel.com>
diff --git a/.travis.yml b/.travis.yml
index 793ab9c..32843f0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,4 +24,7 @@
   - pushd ./build
   - CONFIG_SITE=../lib/default_config.site ../configure --enable-unit
   - make -j$(nproc)
-  - make -j$(nproc) check
+  - make simulator-build
+  - make simulator-start
+  - make check
+  - make simulator-stop