Add exclude regexp filters for pgoperate check PG_CHECK_LOGFILES

[rolandstirnimann]

Currently the pgoperate check module allows to include specific thresholds with the following parameter:

PG_CHECK_LOGFILES_THRESHOLD="ERROR|FATAL|PANIC"

However, it would be helpful to have an additional parameter to exclude specific patterns based on a regexp. Example:
PG_CHECK_LOGFILES_EXCLUDE_PATTERN="<regexp>"

This means the check searches first for the given thresholds and applies then the exclude pattern. Everything that remains afterwards will be treaten as issue.