Arcyd: report total times spent on Git, Conduit

To guide the effort to make Arcyd more scalable, gather data on how much
time we spend doing what; beginning with Git and Conduit.

Test Plan:
inspect $ ./testbed/arcyd/status_html_testbed.sh
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh
Arcyd: provide clone not path to abdt_git.Clone

So that we can instrument usage of phlsys_git.GitClone, change
abdt_git.Clone so that it receives one instead of constructing one of
its own.  This means we can pass it an instrumented one if we wish.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh
Arcyd: time fetching, conduit connect, processing

Add to the general profiling picture by timing 'git fetch',
'conduit connect' and process args.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh
Arcyd: fix arcyd status file unlimited growth

Stop the Arcyd status file from growing with each cycle - update
existing entries for repositories instead of continuously appending to
the list.

Test Plan:
Add 'repeated repo' to dev-status-html
Manually inspect $ ./testbed/arcyd/status_html_testbed.sh
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh