Temporarily replace compute hard reboot by soft reboot test due to BZ1890895
Due to BZ1890895, test_reboot_computes_recovery is not stable. This test
was applying a hard reboot to the compute nodes. The test is replaced by
test_soft_reboot_computes_recovery until BZ1890895 is resolved
Change-Id: If2d68bfbfed3c1b149929ec05a8e83f3720cc174