top: correct, improve and otherwise tweak configs_read

top: correct, improve and otherwise tweak configs_read

This patch addresses the four '-Wunused-result' errors
generated whenever an optimized compile is invoked. It
also made the configs_read() guy a little more robust.

In the process, some logic was rearranged slightly and
some comments were re-indented simply for consistency.

Reference(s):
warning: ignoring return value of 'fgets', declared with attribute warn_unused_result [-Wunused-result]
warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result]

Signed-off-by: Jim Warner <james.warner@comcast.net>