Fix wrong ICE candidate priority calculation

[lherman-cs]

The ice candidate calculation is wrong, the spec uses ^ symbol which represents power. But, in C, this symbol means XOR.

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[MushMal]

Oh wow...

[lherman-cs]

Oh wow...

@MushMal , exactly what I was thinking...

[codecov-commenter]

Codecov Report

Merging #612 into master will decrease coverage by 0.61%.
The diff coverage is 49.67%.

@@            Coverage Diff             @@
##           master     #612      +/-   ##
==========================================
- Coverage   85.46%   84.85%   -0.62%     
==========================================
  Files          41       41              
  Lines        9584     9620      +36     
==========================================
- Hits         8191     8163      -28     
- Misses       1393     1457      +64     

Impacted Files	Coverage Δ
src/source/PeerConnection/PeerConnection.c	84.09% <2.43%> (-5.89%)	⬇️
src/source/PeerConnection/Rtcp.c	43.33% <29.26%> (-7.52%)	⬇️
src/source/Srtp/SrtpSession.c	81.25% <33.33%> (-6.89%)	⬇️
src/source/PeerConnection/Rtp.c	73.71% <80.00%> (+0.06%)	⬆️
src/source/Ice/TurnConnection.c	93.11% <93.61%> (-0.47%)	⬇️
src/source/Ice/ConnectionListener.c	89.94% <100.00%> (-0.51%)	⬇️
src/source/Ice/IceAgent.c	94.92% <100.00%> (ø)
src/source/Ice/Network.c	81.57% <100.00%> (ø)
src/source/Rtcp/RtcpPacket.c	100.00% <100.00%> (ø)
... and 7 more

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