Fix build for linux

Summary:
* Include `unistd.h` for `sleep(3)`
* Include `sys/time.h` for `gettimeofday(3)`
* Include `utils/random.h` for `Random64`

Error messages:

utilities/persistent_cache/hash_table_bench.cc: In constructor ‘rocksdb::HashTableBenchmark::HashTableBenchmark(rocksdb::HashTableImpl<long unsigned int, std::__cxx11::basic_string<char> >*, size_t, size_t, size_t, size_t)’:
utilities/persistent_cache/hash_table_bench.cc:76:28: error: ‘sleep’ was not declared in this scope
       /* sleep override */ sleep(1);
                            ^~~~~
utilities/persistent_cache/hash_table_bench.cc:76:28: note: suggested alternative: ‘strsep’
       /* sleep override */ sleep(1);
                            ^~~~~
                            strsep
utilities/persistent_cache/hash_table_bench.cc: In member function ‘void rocksdb::HashTableBenchmark::RunRead()’:
utilities/persistent_cache/hash_table_bench.cc:107:5: error: ‘Random64’ was not declared in this scope
     Random64 rgen(time(nullptr));
     ^~~~~~~~
utilities/persistent_cache/hash_table_bench.cc:107:5: note: suggested alternative: ‘random_r’
     Random64 rgen(time(nullptr));
     ^~~~~~~~
     random_r
utilities/persistent_cache/hash_table_bench.cc:110:18: error: ‘rgen’ was not declared in this scope
       size_t k = rgen.Next() % max_prepop_key;
                  ^~~~
utilities/persistent_cache/hash_table_bench.cc: In static member function ‘static uint64_t rocksdb::HashTableBenchmark::NowInMillSec()’:
utilities/persistent_cache/hash_table_bench.cc:153:5: error: ‘gettimeofday’ was not declared in this scope
     gettimeofday(&tv, /*tz=*/nullptr);
     ^~~~~~~~~~~~
make[2]: *** [CMakeFiles/hash_table_bench.dir/build.make:63: CMakeFiles/hash_table_bench.dir/utilities/persistent_cache/hash_table_bench.cc.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:3346: CMakeFiles/hash_table_bench.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
Closes https://github.com/facebook/rocksdb/pull/3283

Differential Revision: D6594850

Pulled By: ajkr

fbshipit-source-id: fd83957338c210cdfd253763347aafd39476824f

utilities/persistent_cache/hash_table_bench.cc

@@ -15,11 +15,14 @@ int main() { fprintf(stderr, "Please install gflags to run tools\n"); }
 #include <functional>
 #include <string>
 #include <unordered_map>
+#include <unistd.h>
+#include <sys/time.h>
 
 #include "port/port_posix.h"
 #include "rocksdb/env.h"
 #include "util/gflags_compat.h"
 #include "util/mutexlock.h"
+#include "util/random.h"
 #include "utilities/persistent_cache/hash_table.h"
 
 using std::string;