WIP: remove unnecessary print
Arcyd: fix test_shell to commit configfile changes

Avoid having a dirty working copy in the arcyd/ dir by committing the
generated changes to the configfile before giving control to the user.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/test_shell.sh
    $ cd ../arcyd
    $ git status
Arcyd: fix abdt_fs checks for dirty index

Raise Error classes instead of printing them when the index is
unexpectedly dirty in Accessor.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/test_shell.sh

    # try to remove a repo when index is dirty
    $ cd ../arcyd
    $ arcyd stop
    $ touch blah && git add blah
    $ arcyd rm-repo localhost_fs1_origin
    .. dirty index error ..

    # try to remove a repo when index is clean
    $ git reset
    $ arcyd rm-repo localhost_fs1_origin
    .. ok ..

    # try to add a repo when index is dirty
    $ touch blah && git add blah
    $ arcyd add-repo localhost fs1 origin
    .. dirty index error ..

    # try to add a repo when index is clean
    $ git reset
    $ arcyd add-repo localhost fs1 origin
    .. ok ..