qa/clusters/crimson: increase reactors in fixed-1 cluster

qa/clusters/crimson: increase reactors in fixed-1 cluster

Issue: Various different tests were failing randomly due to slow
ops. There was no common ground between them, it was happening
across differnet object stores (seastore and bluestore) and
across different tests.

Cause: Since this is happening quite randomly, this is likely
happening due to low reactor count.

Solution: We are opting the solution to increase reactors used
for testing. I've increased them to 3 from the initial 2 value.

Fixes: https://tracker.ceph.com/issues/72778
Signed-off-by: Shraddha Agrawal <shraddha.agrawal000@gmail.com>