cfgfile: fix uninitialized variable on load error

cfgfile: fix uninitialized variable on load error

Uninitialized scalar variable.
Using uninitialized value cfg->sections[curr_section]->num_entries
when calling rte_cfgfile_close.
And memory in variables cfg->sections[curr_section],
sect->entries[curr_entry] maybe not equal NULL.
We must decrement counters curr_section, curr_entry when failed to realloc.

Fixes: eaafbad419bf ("cfgfile: library to interpret config files")
Signed-off-by: Dmitriy Yakovlev <bombermag@gmail.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>