send() must return 'int'

[tzaeschke]

DatagramChannel.send() should return an int instead of a Path.

[codecov]

Codecov Report

Attention: Patch coverage is 35.07463% with 87 lines in your changes missing coverage. Please review.

Files	Coverage Δ	Complexity Δ
...n/java/org/scion/jpan/AbstractDatagramChannel.java	84.25% <100.00%> (+0.17%)	74.00 <2.00> (-2.00)	⬆️
...main/java/org/scion/jpan/ScionDatagramChannel.java	82.72% <72.13%> (-13.94%)	24.00 <10.00> (+10.00)	⬇️
src/main/java/org/scion/jpan/PathMetadata.java	0.00% <0.00%> (ø)	0.00 <0.00> (?)