[ci] Set eager-load depending on environment var

because otherwise we also eager load when only running
one single test which increases the boot time.
We only set EAGER_LOAD=1 in Travis CI where we run
the full test suite and the boot time does not matter.

See rails/rails#28736

dist/ci/travis_script.sh

@@ -9,6 +9,7 @@ pushd src/api
 
 if test -z "$SUBTEST"; then
   export DO_COVERAGE=1
+  export EAGER_LOAD=1
   export TESTOPTS="-v"
   case $TEST_SUITE in
     api)

src/api/config/environments/test.rb

@@ -14,6 +14,10 @@
   # and recreated between test runs. Don't rely on the data there!
   config.cache_classes = true
 
+  # We set eager loading to true in Travis CI
+  # to run with the same configuration as in production
+  config.eager_load = ENV.fetch('EAGER_LOAD', '0') == '1'
+
   # Show full error reports and disable caching
   # local requests don't trigger the global exception handler -> set to false
   config.consider_all_requests_local = false