Spindle hangs if NUMA requested and process lacks CAP_SYS_NICE

[nchaimov]

The sched_setaffinity function and related functions used by libnuma require CAP_SYS_NICE. If Spindle is launched in NUMA mode, but lacks this capability, Spindle hangs. Spindle should check whether it has CAP_SYS_NICE and, if not, gracefully degrade rather than hanging. This can be reproduced by running the serial testsuite image with CAP_SYS_NICE removed from docker-compose.yml.