Stop aligning trailing comments which are aligned with the next line.

Previously we would align:
f(); // comment
     // other comment
g();

Even if // other comment was at the start of the line. Now we do not
align trailing comments if they have been already aligned correctly
with the next line.

Thus,
f(); // comment
// other comment
g();
will not be changed, while:
f(); // comment
  // other commment
g();
will lead to the two trailing comments being aligned.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@182577 91177308-0d34-0410-b5e6-96231b3b80d8