transport: clean server URL path

[axw]

Clean the server URL path, so we don't trigger redirects due to non-canonical paths at the server.

Fixes #657

[codecov-io]

Codecov Report

Merging #658 into master will decrease coverage by 0.49%.
The diff coverage is 50%.

@@            Coverage Diff            @@
##           master     #658     +/-   ##
=========================================
- Coverage   88.37%   87.87%   -0.5%     
=========================================
  Files         123      123             
  Lines        7891     7640    -251     
=========================================
- Hits         6974     6714    -260     
- Misses        796      822     +26     
+ Partials      121      104     -17

Impacted Files	Coverage Δ
transport/http.go	95.41% <50%> (+1.14%)	⬆️
model/marshal_fastjson.go	77.1% <0%> (-5.58%)	⬇️
breakdown.go	95.89% <0%> (-3.43%)	⬇️
tracer.go	91.03% <0%> (-0.34%)	⬇️
utils.go	82.69% <0%> (-0.19%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update affcad0...6f3228d. Read the comment docs.