Fix Koa error metrics and Alpine Linux disk metrics

Changed

• Remove route tag from HTTP server spans. Since the span will already have the route attribute as part of its name, the tag is redundant.

• Filter more disk mountpoints for disk usage and disk IO stats. This helps reduce noise in the host metrics by focussing on more important mountpoints.

  The following mountpoint are ignored. Any mountpoint containing:

  • /etc/hostname
  • /etc/hosts
  • /etc/resolv.conf
  • /snap/
  • /proc/

Fixed

• Fix an issue where the method tag extracted from an incoming HTTP request span would be overriden with the method used for an outgoing HTTP request span.
• Support disk usage reporting (using df) on Alpine Linux. This host metric would report an error on Alpine Linux.
• When a disk mountpoint has no inodes usage percentage, skip the mountpoint, and report the inodes information successfully for the inodes that do have an inodes usage percentage.
• Fix missing error metrics for the error rate and error count graphs in some scenarios, like with Koa apps.

See the Node.js 3.0.27 package changelog for more information.