[clang-format] Ensure wrapped ObjC selectors with 1 arg obey IndentWrappedFunctionNames

Summary:
In D43121, @Typz introduced logic to avoid indenting 2-or-more
argument ObjC selectors too far to the right if the first component
of the selector was longer than the others.

This had a small side effect of causing wrapped ObjC selectors with
exactly 1 argument to not obey IndentWrappedFunctionNames:

```
- (aaaaaaaaaa)
aaaaaaaaaa;
```

This diff fixes the issue by ensuring we align wrapped 1-argument
ObjC selectors correctly:

```
- (aaaaaaaaaa)
    aaaaaaaaaa;
```

Test Plan: New tests added. Test failed before change, passed
  after change. Ran tests with:
  % make -j12 FormatTests && ./tools/clang/unittests/Format/FormatTests

Reviewers: djasper, klimek, Typz, jolesiak

Reviewed By: djasper, jolesiak

Subscribers: cfe-commits, Typz

Differential Revision: https://reviews.llvm.org/D44994

llvm-svn: 328871