libglnx porting: delete temp files on failure of file creation

We noticed the temp files being left over in ostree when (mistakenly)
trying to create refs with names in use by folders. This fix removes
temp files created by glnx_file_replace_contents_at on failure.

Closes: #348
Approved by: cgwalters

diff --git a/libglnx b/libglnx
index afe3c3a86178c29ceaa3a5e46397ab2fa97202b3..a6d08657aa868a0d5c7b5dd494e16f65415a148f 160000 (submodule)
--- a/libglnx
+++ b/libglnx
@@ -1 +1 @@
-Subproject commit afe3c3a86178c29ceaa3a5e46397ab2fa97202b3
+Subproject commit a6d08657aa868a0d5c7b5dd494e16f65415a148f