bindings: python: Fix race conditions at arguments access

bindings: python: Fix race conditions at arguments access

rrdtool_argv and rrdtool_argc have to be allocated at each function stack in
order to have copy of variables for each running thread. Note that we call
librrd functions with GIL unlocked, so previously there was simultaneous access
to global rrdtool_argv and rrdtool_argc variables.

Fixes: 8949308812a0 ("Unlock the global thread lock while processing rrd")
Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>