TOOL-1907 fix flaky CI test case

[trapacska]

$ go help testflag

-parallel n
	    Allow parallel execution of test functions that call t.Parallel.
	    The value of this flag is the maximum number of tests to run
	    simultaneously; by default, it is set to the value of GOMAXPROCS.
	    Note that -parallel only applies within a single test binary.
	    The 'go test' command may run tests for different packages
	    in parallel as well, according to the setting of the -p flag
	    (see 'go help build').

$ go help build

	-p n
		the number of programs, such as build commands or
		test binaries, that can be run in parallel.
		The default is the number of CPUs available.

Created a test case run timeline graph with the default settings:

Also created a graph with -p 1:

So it is clearly visible that packages are running in parallel and also that it can be turned off.