optimize system dns

[YangSen-qn]

No description provided.

[codecov]

Codecov Report

Merging #479 (af869ad) into master (18b245a) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #479      +/-   ##
============================================
- Coverage     69.52%   69.44%   -0.08%     
+ Complexity     1312     1310       -2     
============================================
  Files           103      103              
  Lines          6877     6876       -1     
  Branches       1045     1045              
============================================
- Hits           4781     4775       -6     
- Misses         1334     1340       +6     
+ Partials        762      761       -1     

Impacted Files	Coverage Δ
.../main/java/com/qiniu/android/common/Constants.java	0.00% <ø> (ø)
...ain/java/com/qiniu/android/http/dns/SystemDns.java	92.00% <100.00%> (-0.31%)	⬇️
.../main/java/com/qiniu/android/http/dns/HttpDns.java	43.33% <0.00%> (-10.00%)	⬇️
...c/main/java/com/qiniu/android/http/dns/UdpDns.java	40.00% <0.00%> (-3.34%)	⬇️
...main/java/com/qiniu/android/http/ResponseInfo.java	61.44% <0.00%> (-2.41%)	⬇️
...roid/http/request/httpclient/SystemHttpClient.java	72.13% <0.00%> (-0.77%)	⬇️
.../java/com/qiniu/android/utils/FastDatePrinter.java	66.49% <0.00%> (-0.52%)	⬇️
.../qiniu/android/http/request/HttpSingleRequest.java	75.92% <0.00%> (+0.61%)	⬆️
.../com/qiniu/android/collect/UploadInfoReporter.java	66.43% <0.00%> (+2.79%)	⬆️

[YangSen-qn]

done