logalloc_test sometimes fails when the machine is heavily loaded

[denesb]

Just seen a failure that I cannot reproduce. I'm guessing it is timing related. Log attached. logalloc_test.99.log

@michoecho

[avikivity]

The background reclaimer test is inherently timing sensitive. I don't have a good idea how to fix it. Maybe it should be removed from the automated tests.

[benipeled]

We facing this failure ~70% of next-2021.1, If it will not gonna make it difficult later to debug the fall - can we disable this test?

[Annamikhlin]

Failed again in 2021.1 - https://jenkins.scylladb.com/job/enterprise-2021.1/job/build/227/