add getSourceType api

[nobodyiam]

to indicate where the config is loaded from, e.g. remote config service, local cache or failed

[codecov-io]

Codecov Report

Merging #1470 into master will increase coverage by 0.18%.
The diff coverage is 94.87%.

@@             Coverage Diff              @@
##             master    #1470      +/-   ##
============================================
+ Coverage      48.4%   48.59%   +0.18%     
- Complexity     1801     1812      +11     
============================================
  Files           379      380       +1     
  Lines         10930    10956      +26     
  Branches       1121     1122       +1     
============================================
+ Hits           5291     5324      +33     
+ Misses         5253     5245       -8     
- Partials        386      387       +1

Impacted Files	Coverage Δ	Complexity Δ
...rk/apollo/internals/LocalFileConfigRepository.java	70.06% <100%> (+0.83%)	25 <4> (+1)	⬆️
...trip/framework/apollo/internals/DefaultConfig.java	81.44% <100%> (+2.32%)	29 <4> (+3)	⬆️
...ework/apollo/internals/RemoteConfigRepository.java	87.26% <100%> (+0.08%)	22 <1> (+1)	⬆️
...ctrip/framework/apollo/internals/SimpleConfig.java	87.17% <100%> (+1.46%)	8 <4> (+2)	⬆️
...ctrip/framework/apollo/enums/ConfigSourceType.java	83.33% <83.33%> (ø)	2 <2> (?)
...framework/apollo/internals/AbstractConfigFile.java	86.2% <83.33%> (-0.59%)	11 <2> (+1)
...ervice/service/ReleaseMessageServiceWithCache.java	85.71% <0%> (-1.2%)	24% <0%> (-1%)
...lo/configservice/util/InstanceConfigAuditUtil.java	70.17% <0%> (-0.88%)	13% <0%> (-1%)
...rip/framework/apollo/internals/AbstractConfig.java	81.85% <0%> (+0.84%)	50% <0%> (+1%)	⬆️
... and 2 more

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[coveralls]

Coverage increased (+0.1%) to 52.127% when pulling 17236f1 on nobodyiam:config-source into ffc99dd on ctripcorp:master.