fix for java 11

[nobodyiam]

What's the purpose of this PR

Fix the java 11 compatibility issue brought by #2828

Brief changelog

use guava base64 instead of javax.xml.bind.DatatypeConverter to support java 11

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[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@fb9b24a). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #2888   +/-   ##
=========================================
  Coverage          ?   50.69%           
  Complexity        ?     2150           
=========================================
  Files             ?      425           
  Lines             ?    13055           
  Branches          ?     1337           
=========================================
  Hits              ?     6618           
  Misses            ?     5969           
  Partials          ?      468

Impacted Files	Coverage Δ	Complexity Δ
...framework/apollo/core/signature/HmacSha1Utils.java	62.5% <100%> (ø)	1 <0> (?)

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[coveralls]

Coverage increased (+0.04%) to 54.278% when pulling 79e8400 on nobodyiam:fix-java-11 into fb9b24a on ctripcorp:master.