test: fix call to virFDStreamOpenFile in testDomainScreenshot

N.B.  This had no ill effects as long as O_RDONLY is defined to
      to be 0, such that the expression (O_RDONLY < 0) yielded 0
      again.
Signed-off-by: NClaudio Bley <cbley@av-test.de>

src/test/test_driver.c

@@ -5862,7 +5862,7 @@ testDomainScreenshot(virDomainPtr dom ATTRIBUTE_UNUSED,
     if (VIR_STRDUP(ret, "image/png") < 0)
         return NULL;
 
-    if (virFDStreamOpenFile(st, PKGDATADIR "/libvirtLogo.png", 0, 0, O_RDONLY < 0))
+    if (virFDStreamOpenFile(st, PKGDATADIR "/libvirtLogo.png", 0, 0, O_RDONLY) < 0)
         VIR_FREE(ret);
 
     return ret;