Fixes #1194 error reading 4.5.5 tpr files with dihres

Somehow the tpx_version produced by 4.5.5 was higher (73)
than expected, making the the tpx reading incorrectly
assuming this was using the new file format.
Now set to the version before the
first official 4.6 tpx format, 82 to match the tpr files
in the regression tests. Duh!

Change-Id: I40d8ffa0d350cf3b690f8dfb071fc191f027d02f