[test] coverity: only run make test if not running coverity tests

.travis.yml

@@ -12,7 +12,7 @@ install:
   - sudo apt-get install -y paparazzi-dev paparazzi-jsbsim gcc-arm-embedded libipc-run-perl cmake
 script:
   - arm-none-eabi-gcc --version
-#  - make test
+  - if [ "${COVERITY_SCAN_BRANCH}" != 1 ]; then make test; fi
 
 env:
   global: