Dns local cache

[YangSen-qn]

No description provided.

[codecov]

Codecov Report

Merging #404 into master will increase coverage by 1.13%.
The diff coverage is 24.13%.

@@             Coverage Diff              @@
##             master     #404      +/-   ##
============================================
+ Coverage     55.71%   56.85%   +1.13%     
- Complexity      471      475       +4     
============================================
  Files            46       46              
  Lines          3604     3576      -28     
  Branches        498      491       -7     
============================================
+ Hits           2008     2033      +25     
+ Misses         1334     1282      -52     
+ Partials        262      261       -1     

Impacted Files	Coverage Δ	Complexity Δ
.../main/java/com/qiniu/android/common/Constants.java	0.00% <ø> (ø)	0.00 <0.00> (ø)
...qiniu/android/storage/persistent/DnsCacheFile.java	9.61% <0.00%> (+2.47%)	1.00 <0.00> (ø)
...ain/java/com/qiniu/android/http/DnsPrefetcher.java	46.51% <19.04%> (+2.31%)	26.00 <0.00> (ø)
...va/com/qiniu/android/http/custom/DnsCacheInfo.java	38.09% <42.85%> (ø)	3.00 <2.00> (?)
...n/java/com/qiniu/android/storage/FormUploader.java	68.02% <0.00%> (+0.68%)	13.00% <0.00%> (+1.00%)
.../java/com/qiniu/android/utils/FastDatePrinter.java	37.40% <0.00%> (+1.03%)	41.00% <0.00%> (+3.00%)
.../java/com/qiniu/android/storage/UploadOptions.java	65.11% <0.00%> (+2.32%)	10.00% <0.00%> (+1.00%)
...main/java/com/qiniu/android/utils/StringUtils.java	62.37% <0.00%> (+20.79%)	15.00% <0.00%> (+2.00%)