fs: two minor optimizations

1. If the function in tryStatSync threw, it would never reach that code path to return any value.
2. Only use try catch if necessary. lchmodSync does not need the second try catch in most cases.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

fs