[go_expvar] Fix path tag appended to all metrics matching path regex

[zippolyte]

What does this PR do?

Fix bug where each path matching the path regex of a metric would be added as a tag when an alias is set.
This would result in something like this :

 ('scheduler.queues.size',
  1497030010,
  1,
  {'hostname': 'mac-agent5',
   'tags': ['check_type:python',
            'expvar_url:http://localhost:5000/debug/vars',
            'path:scheduler.Queues.0.Size',
            'path:scheduler.Queues.1.Size'],
   'type': 'gauge'}),
 ('scheduler.queues.size',
  1497030010,
  2,
  {'hostname': 'mac-agent5',
   'tags': ['check_type:python',
            'expvar_url:http://localhost:5000/debug/vars',
            'path:scheduler.Queues.0.Size',
            'path:scheduler.Queues.1.Size'],
   'type': 'gauge'})

instead of this :

 ('scheduler.queues.size',
  1497030010,
  1,
  {'hostname': 'mac-agent5',
   'tags': ['check_type:python',
            'expvar_url:http://localhost:5000/debug/vars',
            'path:scheduler.Queues.0.Size]',
   'type': 'gauge'}),
 ('scheduler.queues.size',
  1497030010,
  2,
  {'hostname': 'mac-agent5',
   'tags': ['check_type:python',
            'expvar_url:http://localhost:5000/debug/vars',
            'path:scheduler.Queues.1.Size'],
   'type': 'gauge'})

for this yaml file :

- path: scheduler/Queues/\d+/Size
   type: gauge
   alias: scheduler.queues.size

Motivation

Discovered the bug while testing the scheduler in the new agent.

Testing Guidelines

An overview on testing
is available in our contribution guidelines.

Versioning

• Bumped the version check in manifest.json
• Updated CHANGELOG.md

Additional Notes

Anything else we should know when reviewing?

[olivielpeau]

Code LGTM! 👌

One comment on the changelog. Could you update manifest.json with the version bump too?

[olivielpeau]

could you put this line in a new 1.0.3 section? 1.0.2 is what was shipped with 5.14.0