Avoid method call if `@transaction_state` is not finalized

Method call in Ruby is a bit slow.

This makes attribute access 10% faster by avoiding method call
(`sync_with_transaction_state`).

Before (96cf7e0e):

```
Warming up --------------------------------------
             user.id   131.291k i/100ms
          user['id']    91.786k i/100ms
           user.name   151.605k i/100ms
        user['name']    92.664k i/100ms
       user.changed?    17.772k i/100ms
 user.saved_changes?    23.909k i/100ms
Calculating -------------------------------------
             user.id      1.988M (± 7.0%) i/s -      9.978M in   5.051474s
          user['id']      1.155M (± 5.8%) i/s -      5.783M in   5.022672s
           user.name      2.450M (± 4.3%) i/s -     12.280M in   5.021234s
        user['name']      1.263M (± 2.1%) i/s -      6.394M in   5.066638s
       user.changed?    175.070k (±13.3%) i/s -    853.056k in   5.011555s
 user.saved_changes?    259.114k (±11.8%) i/s -      1.267M in   5.001260s
```

After (this change):

```
Warming up --------------------------------------
             user.id   137.625k i/100ms
          user['id']    96.054k i/100ms
           user.name   156.379k i/100ms
        user['name']    94.795k i/100ms
       user.changed?    18.172k i/100ms
 user.saved_changes?    24.337k i/100ms
Calculating -------------------------------------
             user.id      2.201M (± 0.5%) i/s -     11.010M in   5.002955s
          user['id']      1.320M (± 1.0%) i/s -      6.628M in   5.021293s
           user.name      2.677M (± 1.6%) i/s -     13.449M in   5.024399s
        user['name']      1.314M (± 1.8%) i/s -      6.636M in   5.051444s
       user.changed?    190.588k (±11.1%) i/s -    944.944k in   5.065848s
 user.saved_changes?    262.782k (±12.1%) i/s -      1.290M in   5.028080s
```

0 files changed, 0 insertions, 0 deletions