Fix incorrect 'unlink' return value check

Change-Id: I430f6bb21a5fd87e0422420463e8bb96c4a612e1
diff --git a/partition.cpp b/partition.cpp
index 1f57a53..543e867 100644
--- a/partition.cpp
+++ b/partition.cpp
@@ -2124,7 +2124,7 @@
 				}
 				rmdir(dir.c_str());
 			} else if (de->d_type == DT_REG || de->d_type == DT_LNK || de->d_type == DT_FIFO || de->d_type == DT_SOCK) {
-				if (!unlink(dir.c_str()))
+				if (unlink(dir.c_str()) != 0)
 					LOGINFO("Unable to unlink '%s': %s\n", dir.c_str(), strerror(errno));
 			}
 		}