test: adapt to output change from 10e162bb9bf5
The changeset 10e162bb9bf5 in code extend the list of capabilities to include
"phases=['heads']" this has a minor impact on test output
CORE-TEST-OUTPUT-UPDATE: 10e162bb9bf5
stack: handle basic case of splitting with crash
hg stack used to crash horribly whenever a split was encountered. This is no
longer the case.
If the result of the split (or there successors) produce a sensible linear
result with on final head, we can just assume that head is the evolution
destination.