Fix for PROTON-1517

[aikchar]

Fixes the bug reported in PROTON-1517.

[ssorj]

@aikchar , I applied this patch. Please close when you get a chance.

2b03394

[codecov-io]

Codecov Report

Merging #110 into master will decrease coverage by 0.35%.
The diff coverage is 68.19%.

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
- Coverage   78.67%   78.31%   -0.36%     
==========================================
  Files         231      232       +1     
  Lines       30546    30687     +141     
  Branches     2903     2927      +24     
==========================================
+ Hits        24033    24034       +1     
- Misses       4872     4912      +40     
- Partials     1641     1741     +100

Impacted Files	Coverage Δ
proton-c/bindings/cpp/src/scalar_test.hpp	100% <ø> (ø)
examples/c/send-ssl.c	76.28% <ø> (ø)	⬆️
examples/c/send.c	75.82% <ø> (ø)	⬆️
proton-c/bindings/cpp/src/connection_driver.cpp	77.77% <ø> (ø)
examples/cpp/multithreaded_client.cpp	81.81% <ø> (ø)	⬆️
examples/c/send-abort.c	76.34% <ø> (ø)	⬆️
examples/c/direct.c	83.63% <ø> (ø)	⬆️
proton-c/bindings/cpp/src/types_internal.hpp	94.73% <ø> (ø)
proton-c/src/core/message.c	59.53% <ø> (-0.78%)	⬇️
examples/cpp/ssl_client_cert.cpp	81.08% <ø> (ø)	⬆️
... and 71 more

---

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[dmitrytokarev]

@ssorj why didn't you just merge this PR?
Now @aikchar doesn't get credit for his work.

[ssorj]

@dmitrytokarev , I was failing at making it merge the way I wanted. I will try to figure out the right sequence of commands so I get it right next time.

[jirkadanek]

whoa, codecov.io has gone crazy... this report above includes about 10 recent commits to master, not just this one...

@dmitrytokarev Is committing as myself, but setting git commit --author "Other person <other@person.edu>" acceptable GitHub practice? Or doing a final commit --amend with the --author set? This is what I intended to do (in my personal project...)

[dmitrytokarev]

@jdanekrh well it doesn't really matter how it's done as long as community contributions are authored and recognized. Some people may show case their github accounts on their resumes, so if they don't get credit for their work, they have nothing to showcase.