Traceroute between tunnels: use GRE ip protocol

[progwriter]

The flow construction todo fell through the cracks. Not using GRE protocol means interface ACLs would prevent tunnel edges from coming up

[batfish-bot]

This change is 

[dhalperi]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[progwriter]

Reviewed 1 of 1 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[codecov]

Codecov Report

Merging #6521 (72877e8) into master (24a8dad) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #6521      +/-   ##
============================================
- Coverage     73.36%   73.34%   -0.03%     
+ Complexity    35605    35590      -15     
============================================
  Files          2830     2830              
  Lines        143737   143738       +1     
  Branches      17365    17365              
============================================
- Hits         105455   105425      -30     
- Misses        29937    29956      +19     
- Partials       8345     8357      +12     

Impacted Files	Coverage Δ	Complexity Δ
...java/org/batfish/common/topology/TopologyUtil.java	90.99% <100.00%> (+0.02%)	157.00 <0.00> (ø)
...g/batfish/datamodel/flow/IncomingSessionScope.java	84.61% <0.00%> (-15.39%)	7.00% <0.00%> (-1.00%)
...batfish/representation/aws/LoadBalancerTarget.java	54.16% <0.00%> (-4.17%)	8.00% <0.00%> (-1.00%)
.../org/batfish/dataplane/rib/RouteAdvertisement.java	83.67% <0.00%> (-4.09%)	18.00% <0.00%> (-1.00%)
...ain/java/org/batfish/symbolic/IngressLocation.java	65.78% <0.00%> (-2.64%)	15.00% <0.00%> (-1.00%)
...l/src/main/java/org/batfish/datamodel/FibImpl.java	88.52% <0.00%> (-2.46%)	29.00% <0.00%> (-1.00%)
...col/src/main/java/org/batfish/role/InferRoles.java	89.54% <0.00%> (-1.37%)	50.00% <0.00%> (-1.00%)
...main/java/org/batfish/datamodel/acl/AclTracer.java	60.37% <0.00%> (-1.26%)	43.00% <0.00%> (-1.00%)
...src/main/java/org/batfish/coordinator/PoolMgr.java	59.52% <0.00%> (-1.20%)	15.00% <0.00%> (-1.00%)
...src/main/java/org/batfish/coordinator/WorkMgr.java	75.42% <0.00%> (-0.55%)	245.00% <0.00%> (-3.00%)
... and 3 more