Refactor, use __call__() instead of call()

There are a few classes in the code base which allow 'passing through'
of commands to another API or interface by supplying a 'call' method,
e.g.

    git_repo.call('status')

Python allows classes to be 'callable' by suppling a '__call__' method,
which is usable like so:

    git_repo('status')

This is shorter and seems to be just as clear as providing an explicit
'call' method.  It also has the benefit of making it a bit easier to
mock up such classes by making it possible to pass functions in their
stead.

Change phlsys_conduit, phlsys_repo and abdi_repo to provide '__call__'
instead of 'call'.  Fix up all existing references to '.call('.

All three classes are modified in one commit so it's easier to
mechanically replace usage and verify the changes, i.e.

  $ git grep '\.call('
  $ find py -iname '*.py' | xargs sed -i 's/\.call(/(/g'
  $ git grep '\.call('

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh
$ ./testbed/arcyon/acceptance_tests.sh
abdt_branch*: remove unused 'get_clone' method

Test Plan:
$ git grep get_clone
$ ./precommit.sh
abdt_branch: refactor, rename 'clone' -> 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_branch as well.

Test Plan:
$ ./precommit.sh
abdi_repo: fix doc typo 'paht'->'path'
abdt_branch__t: refactor, rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_branch__t as well.

Test Plan:
search for 'clone' in abdt_branch__t
$ ./precommit.sh
abdt_differ: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_differ too.

Test Plan:
search for 'clone' in abdt_differ
$ ./precommit.sh
abdt_git: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_git too.

Test Plan:
search for 'clone' in abdt_git
$ ./precommit.sh
abdt_git__t: rename 'clone' to 'repo'

the rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_git__t too.

Test Plan:
search for 'clone' in abdt_git__t
$ ./precommit.sh
abdt_lander: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_lander too.

Test Plan:
search for 'clone' in abdt_lander
$ ./precommit.sh
abdt_landinglog: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update abdt_landinglog too.

Test Plan:
search for 'clone' in abdt_landinglog
$ ./precommit.sh
barcmd_gc: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update barcmd_gc too.

Test Plan:
search for 'clone' in barcmd_gc
$ ./precommit.sh
gabcmd_gitphablog: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update gabcmd_gitphablog too.

Test Plan:
search for 'clone' in gabcmd_gitphablog
$ ./precommit.sh
phlgit_branch: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_branch too.

Test Plan:
search for 'clone' in phlgit_branch
$ ./precommit.sh
phlgit_checkout: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_checkout too.

Test Plan:
search for 'clone' in phlgit_checkout
$ ./precommit.sh
phlgit_diff: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_diff too.

Test Plan:
search for 'clone' in phlgit_diff
$ ./precommit.sh
phlgit_hashobject: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_hashobject too.

Test Plan:
search for 'clone' in phlgit_hashobject
$ ./precommit.sh
phlgit_log: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_log too.

Test Plan:
search for 'clone' in phlgit_log
$ ./precommit.sh
phlgit_log__t: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_log__t too.

Test Plan:
search for 'clone' in phlgit_log__t
$ ./precommit.sh
phlgit_merge: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_merge too.

Test Plan:
search for 'clone' in phlgit_merge
$ ./precommit.sh
phlgit_push: rename 'clone' to 'repo'

The rest of the code base has standardised on 'repo' as the name for a
git repository, update phlgit_push too.

Test Plan:
search for 'clone' in phlgit_push
$ ./precommit.sh