fix qmd.x error when print(molecular dipolemoment) is enabled with static sampling properties

[VaradRengaraj]

For an MD simulation, when I enabled the print for molecular dipole moment (the last 1 in the print option), along with static sampling steps (ng), it resulted in a qmd.x crash.

On further debugging the source code, I observed that in the function "md_static_prepare_traj" at line 110, the string "file_position" is again passed in quotes "". This was resulting in a qmd.x crash with the following error message: "Bad POSITION parameter in"

I have made a small fix for this typo error and found the qmd.x working for the given scenario.

Input_water_acmd.txt

[VaradRengaraj]

For the given input text file, I observed a very large amount of memory being consumed by the function computing RDFs, finally resulting in the qmd.x crash.
On debugging that issue, I found that there were some memory leaks in the kinetic_acmd() and dynamics() functions. Though these memory leaks are not related to the memory problem associated with the RDF computing function, I thought it is better to fix these issues.