syscalls/lseek11.c: fix syncfs() && SEEK_DATA

1) We add SAFE_FSYNC().
2) Compilation failed on RHEL6.9GA because syncfs() was not defined.
   this function is introduced since linux 2.6.39, so we could use
   SAFE_FSYNC() instead of syncfs().
3) We add a check if SEEK_DATA was implemented in get_blocksize(),
   and remove this check in setup().

Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
diff --git a/lib/safe_macros.c b/lib/safe_macros.c
index df0df7f..bffc5a1 100644
--- a/lib/safe_macros.c
+++ b/lib/safe_macros.c
@@ -874,3 +874,17 @@
 
 	return rval;
 }
+
+int safe_fsync(const char *file, const int lineno, int fd)
+{
+	int rval;
+
+	rval = fsync(fd);
+
+	if (rval) {
+		tst_brkm(TBROK | TERRNO, NULL,
+			"%s:%d: fsync(%i) failed", file, lineno, fd);
+	}
+
+	return rval;
+}