Use the current port rather than hardcoding 8080

[mattsheppard]

I initially wanted to use @LocalServerPort like AbstractIntegrationTest
does, but got execeptions from Spring. This approach is based
on http://stackoverflow.com/a/36391145/797

Fixes #19

[codecov-io]

Codecov Report

Merging #20 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master      #20      +/-   ##
============================================
+ Coverage     93.83%   93.84%   +0.01%     
  Complexity      130      130              
============================================
  Files            24       24              
  Lines           454      455       +1     
  Branches          5        5              
============================================
+ Hits            426      427       +1     
  Misses           25       25              
  Partials          3        3

Impacted Files	Coverage Δ	Complexity Δ
...p/src/main/java/mujina/idp/MetadataController.java	100% <100%> (ø)	3 <0> (ø)	⬇️

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