Ply abort when we git am --abort under the hood

[rconradharris]

rick@nova-dev:~/Documents/code/openstack/nova$ ply abort
Traceback (most recent call last):
File "/home/rick/.virtualenvs/openstack/bin/ply", line 9, in
load_entry_point('plypatch==0.3.5', 'console_scripts', 'ply')()
File "/home/rick/Documents/code/openstack/ply/plypatch/cli.py", line 271, in main
args.func(args)
File "/home/rick/Documents/code/openstack/ply/plypatch/cli.py", line 69, in do
self.working_repo.abort()
File "/home/rick/Documents/code/openstack/ply/plypatch/init.py", line 249, in abort
self._resolve_conflict('abort')
File "/home/rick/Documents/code/openstack/ply/plypatch/init.py", line 236, in _resolve_conflict
self.am(**kwargs)
File "/home/rick/Documents/code/openstack/ply/plypatch/git/init.py", line 14, in wrapper
return fn(self, _args, *_kwargs)
File "/home/rick/Documents/code/openstack/ply/plypatch/git/init.py", line 73, in am
raise exc.PatchDidNotApplyCleanly
plypatch.git.exc.PatchDidNotApplyCleanly

If we manually resolved an am we stlil a way to ply resolve or ply abort.

Looks like am --abort returns an error (since there is nothing to abort) and this raises a PatchDidNotApplyCleanly exception. Solution is to catch that error and raise NothingToAbort, then have restore handle that.