Use urandom instead of random
Use urandom instead of random

I found that "variable.32-bit tracepoint arg" runtime test fails on
Linux 5.6 rc5. It turns out that Linux 5.6 changes the behavior of
/dev/random and now it behaves almost like urandom, and
trace_urandom_read() is called instead of trace_random_read():

https://github.com/torvalds/linux/commit/30c08efec8884fb106b8e57094baa51bb4c44e32

Use urandom instead of random so that the test runs on a new kernel.

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace