PERF: fixed int64 indexing perf issue when conversion to int64

[jreback]

fixes an issue I when using non-int64 Int64Indexes (which is very rare) anyhow

-------------------------------------------------------------------------------
Test name                                    | head[ms] | base[ms] |  ratio   |
-------------------------------------------------------------------------------
timeseries_large_lookup_value                |   0.0213 |   2.5117 |   0.0085 |
Ratio < 1.0 means the target commit is faster then the baseline.
Seed used: 1234

Target [0933ba3] : PERF: fixed int64 indexing perf issue when conversion to int64
Base   [8f92d9a] : Merge PR #2881 and fix unit test

[jreback]

fixes this bench in #3326, I think was introduced in #3322