Set hits to 0 for inline block's JITMethodInfo

This fixes the following valgrind error:

    ==13303== Thread 4:
    ==13303== Conditional jump or move depends on uninitialised value(s)
    ==13303==    at 0x7826ED: rubinius::Inliner::inline_for_class(rubinius::Class*, int) (inline.cpp:159)
    ==13303==    by 0x782312: rubinius::Inliner::consider_mono() (inline.cpp:35)
    ==13303==    by 0x7A9EFE: rubinius::JITVisit::visit_send_stack(unsigned long, unsigned long) (jit_visit.hpp:1481)
    ==13303==    by 0x7A1CD6: rubinius::VisitInstructions<rubinius::JITVisit>::dispatch(int) (jit_visit.hpp:1565)
    ==13303==    by 0x7A1426: rubinius::jit::Walker::call(rubinius::OpcodeIterator&) (jit_builder.cpp:554)
    ==13303==    by 0x7A11B4: void rubinius::jit::ControlFlowWalker::run<rubinius::jit::Walker>(rubinius::jit::Walker&) (control_flow.hpp:49)
    ==13303==    by 0x79FB30: rubinius::jit::Builder::generate_body() (jit_builder.cpp:591)
    ==13303==    by 0x788576: rubinius::Inliner::emit_inline_block(rubinius::JITInlineBlock*, llvm::Value*) (inline.cpp:648)
    ==13303==    by 0x78809A: rubinius::Inliner::inline_block(rubinius::JITInlineBlock*, llvm::Value*) (inline.cpp:284)
    ==13303==    by 0x7AD231: rubinius::JITVisit::visit_yield_stack(unsigned long) (jit_visit.hpp:2709)
    ==13303==    by 0x7A1E55: rubinius::VisitInstructions<rubinius::JITVisit>::dispatch(int) (instruction_visitors.hpp:62)
    ==13303==    by 0x7A1426: rubinius::jit::Walker::call(rubinius::OpcodeIterator&) (jit_builder.cpp:554)
    ==13303==

This valgrind error is introduced by this commit:

a787d839d88e8542d573f966b82f4376a0858ed4
    Don't inline calls for not often called methods
Merge pull request #2235 from ryoqun/valgrind-error-hits

Set hits to 0 for inline block's JITMethodInfo