[test] test_measurements_for_metric need to be corrected

[Jose Perez Carranza]

Brief Description
-----------------
Test test_measurements_for_metric [1] need to be re-designed to the current functionality of STX deployment.

1- https://opendev.org/starlingx/test/src/branch/master/automated-pytest-suite/testcases/functional/ceilometer/test_ceilometer_statistics.py#L42

Severity
--------
Provide the severity of the defect.
Minor

Steps to Reproduce
------------------
Run pytest test suite as follows:

$ pytest -m sanity --testcase-config=config.conf testcases/functional/ceilometer/test_ceilometer_statistics.py::test_measurements_for_metric[image.size]

Expected Behavior
------------------
TC should be executed correctly and be reported as PASS

Actual Behavior
----------------
TC is reporting a FAIL

Reproducibility
---------------
100%

System Configuration
--------------------
 Multi-node system, Standartd 2+2

Branch/Pull Time/Commit
-----------------------
###
### StarlingX
### Release 19.08
###

OS="centos"
SW_VERSION="19.08"
BUILD_TARGET="Host Installer"
BUILD_TYPE="Formal"
BUILD_ID="r/stx.2.0"

JOB="STX_BUILD_2.0"
<email address hidden>"
BUILD_NUMBER="40"
BUILD_HOST="starlingx_mirror"
BUILD_DATE="2019-08-26 23:30:00 +0000"

Last Pass
---------
First time executing this this Test Case at local infrastructure.

Timestamp/Logs
--------------
> assert False, output
E AssertionError: internal endpoint for metric service in RegionOne region not found
E assert False

Test Activity
-------------
Enablement of automated-pytest-suite.

[Ghada Khalil (gkhalil)]

minor issue w/ test automation framework; not gating, but would be nice to fix