Arcyd: assert branchmock argspec matches branch

Use inspect.getargspec to assert that the argspec of abdt_branchmock
matches that of abdt_branch.

Fix up places where it is not.

Test Plan: $ ./precommit.sh
Arcyd: test mockbranch and branch docstrings match

Use 'inspect.getdoc' to assert that mockbranch and branch docstrings
match.

Fixup instances where they don't match.

Test Plan: $ ./precommit.sh
Arcyd: use new phlsys_compiface to test branchmock

Test that branchmock matches branch using the new phlsys_compiface,
(extracted from abdt_branchmock__t)

Expand check_no_dead_files.sh to check the deps of deps of test drivers.

Test Plan: $ ./precommit.sh
Manually fiddle with branchmock to verify that inconsistencies are
detected.