Ignore test files in coverage calculation

[AAlon]

Issue #, if available:

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #42 into master will decrease coverage by 7.7%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #42      +/-   ##
==========================================
- Coverage   89.03%   81.33%   -7.71%     
==========================================
  Files          16       11       -5     
  Lines         830      375     -455     
==========================================
- Hits          739      305     -434     
+ Misses         91       70      -21

Flag	Coverage Δ
#ROS_1	81.33% <ø> (-7.71%)	⬇️
#ROS_2	81.23% <ø> (-10.1%)	⬇️
#dashing	81.23% <ø> (-10.1%)	⬇️
#kinetic	81.36% <ø> (-7.77%)	⬇️
#melodic	81.23% <ø> (-10.1%)	⬇️

Impacted Files	Coverage Δ
...k_utils/auth/service_credentials_provider_test.cpp
...t/sdk_utils/client_configuration_provider_test.cpp
...mon/test/sdk_utils/logging/aws_log_system_test.cpp
..._common/test/sdk_utils/throttling_manager_test.cpp
...clude/aws_common/sdk_utils/parameter_reader_mock.h

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