CI: reduce build time for Travis valgrind

[nickaein]

• What is the issue you have?

On Travis CI, the current build time for Valgrind job is ~45 minutes which is close to 50 min limit. Hence, a timeout can be triggered when build machines are on heavy load or more tests are added in future.

By skimming through the build log, these unit-tests are the major culprits by spending a lot of time:

Test	Time (~minutes)
regression_valgrind	8
test-large_json_valgrind	8
inspection_valgrind	7
test-unicode_all	7
Total	30

The first three tests takes a long time only on their *_valgrind build mode. This is probably due to high number of memory allocations which makes the job of valgrind harder to check for memory leaks.

The test-unicode_all test however is infamous for taking lot of time to run.

• What is the expected behavior?

The build time for Valgrind job should be reduced to a reasonable value so it does't fail occasionally. This can be done by either skipping some redundant unit-tests, or optimizing them, or requesting a bigger time limit from Travis for this project.

• Which compiler and operating system are you using? Is it a supported compiler?

• Did you use a released version of the library or the version from the develop branch?

• If you experience a compilation error: can you compile and run the unit tests?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.