store: reuse direncoded path in _hybridencode
For a netbeans clone on Windows 7 x64:
Before:
$ hg perffncacheencode
! wall 3.516000 comb 3.525623 user 3.525623 sys 0.000000 (best of 3)
After:
$ hg perffncacheencode
! wall 3.443000 comb 3.447622 user 3.447622 sys 0.000000 (best of 3)
(binary:application/octet-stream)