[TREEPROCMT] Avoid needless reconstruction of TChains
[TREEPROCMT] Avoid needless reconstruction of TChains

...when we are using global entry numbers and therefore each
thread-local TChain has already been constructed with all files.

karies/root,olifre/root,olifre/root,olifre/root,karies/root,karies/root,olifre/root,root-mirror/root,karies/root,olifre/root,root-mirror/root,olifre/root,karies/root,karies/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,karies/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,karies/root,olifre/root,karies/root