[master] remove unused code, reported by Clang Static Analyzer

from Clang Static Analyzer:
Dead Increment
Value stored to 'argv' is never read

(This was just a step that is commonly used per getopt docs.)

Okayed via jabber.

src/lib/bench/example/search_bench.cc

@@ -116,7 +116,6 @@ main(int argc, char* argv[]) {
         }
     }
     argc -= optind;
-    argv += optind;
     if (argc != 0) {
         usage();
     }

src/lib/datasrc/memory/benchmarks/rdata_reader_bench.cc

@@ -183,7 +183,6 @@ main(int argc, char* argv[]) {
         }
     }
     argc -= optind;
-    argv += optind;
     if (argc != 0) {
         usage();
     }

src/lib/datasrc/memory/benchmarks/rrset_render_bench.cc

@@ -179,7 +179,6 @@ main(int argc, char* argv[]) {
         }
     }
     argc -= optind;
-    argv += optind;
     if (argc != 0) {
         usage();
     }

src/lib/dns/benchmarks/message_renderer_bench.cc

@@ -145,7 +145,6 @@ main(int argc, char* argv[]) {
         }
     }
     argc -= optind;
-    argv += optind;
     if (argc != 0) {
         usage();
     }