Fix bench_bitcoin

[vertiond]

Compiling without --disable-bench builds a bench_bitcoin binary which hasn't been ported for VTC yet.

~/github/VTCDocker/output/x86_64-linux-gnu/bin$ ./bench_bitcoin 
Warning, results might be unstable:
* CPU frequency scaling enabled: CPU 0 between 2,200.0 and 3,400.0 MHz
* CPU governor is 'ondemand' but should be 'performance'
* Turbo is enabled, CPU frequency will fluctuate

Recommendations
* Use 'pyperf system tune' before benchmarking. See https://github.com/vstinner/pyperf

|               ns/op |                op/s |    err% |     total | benchmark
|--------------------:|--------------------:|--------:|----------:|:----------
|       18,315,918.00 |               54.60 |    0.4% |      0.20 | `AddrManAdd`
|        1,066,201.00 |              937.91 |    0.6% |      0.01 | `AddrManGetAddr`
|      100,575,880.00 |                9.94 |    1.1% |      0.50 | `AddrManGood`
|              245.74 |        4,069,264.07 |    1.6% |      0.00 | `AddrManSelect`
terminate called after throwing an instance of 'std::runtime_error'
  what():  Verthash datafile not found
Aborted (core dumped)