Update go-ucfg to 0.7.0

[urso]

This introduces:

• (*common.Config).Has: check for setting or namespace by path (can walk
  a configuration)
• (*common.Config).Remove: remove a configuration.

Note: removing from dynamically parsed objects (e.g. parsed objects by
splicing in a custom string via environment variable) is not possible.

[ph]

LGTM

The error look to be with metricbeat, I haven't seen this one before most likely a red herring.

======================================================================
FAIL: MySQL module outputs an event.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/go/src/github.com/elastic/beats/metricbeat/tests/system/test_mysql.py", line 37, in test_status
    self.assertItemsEqual(self.de_dot(MYSQL_FIELDS), evt.keys())
AssertionError: Element counts were not equal:
First has 1, Second has 0:  'mysql'
First has 0, Second has 1:  u'error'
-------------------- >> begin captured logging << --------------------
compose.config.config: DEBUG: Using configuration files: ./docker-compose.yml
docker.utils.config: DEBUG: Trying paths: ['/root/.docker/config.json', '/root/.dockercfg']