Minor change to match naming convention in other collectors.
Initialize the proc or sys FS instance once while initializing
each collector instead of re-creating for each metric update.
Signed-off-by: Paul Gier <pgier@redhat.com>
The cpu frequency information is not always needed and/or available.
This change allows the cpu frequency metrics to be enabled/disabled
separately from the other cpu metrics, and also prevents a frequency
metric failure (such as a parse error) from failing the main cpu
collector.
Fixes#1241
Signed-off-by: Paul Gier <pgier@redhat.com>
