test: exit code depends on checking test plan

TAP tests could be running by test-run.py, but it is often convenient to
run these tests by tarantool only: tarantool test/app-tap/yaml.test.lua.
Most TAP tests returns non-zero exit code when TAP asserts are failed.
But exit code is not changed when TAP plan is bad (number of planned
testcases is not equal to executed). Proposed patch adds test:check() to
TAP tests so tests will return non-zero exit code when plan is bad.

NO_CHANGELOG=it is not a user-visible change
NO_DOC=tests