Compilation find file fix

How to reproduce:

In GNU Emacs 24.4.1 on OS X installed by Macports with projectile from git, create a maven Java project with test failures that output a Java stacktrace, run M-x compile RET mvn install RET to compile and run the tests.

You'll get a *compilation* buffer that has the filenames and line numbers highlighted in the Java stacktrace, but don't list a path to the filename.  Select one of the highlighted filename/line items in the stacktrace.

Expected result:

Jumps right to file and line in project.

Observed result:

Error message in mini-buffer: "No buffer named /full/path/to/java/file/here.java"

Patch:

The compilation-find-file defadvice seems to return a buffer (returned by find-file-noselect run on the filename) in some cases, and in other cases, returns a filename string directly.  This patch fixes it to return a buffer in both scenarios.

Disclaimer:

I'm an elisp newbie, so if I just have a bogus setup, let me know :)