libsupport: fix error handling in quota_write_inode

libsupport: fix error handling in quota_write_inode

The error return value of quota_file_create() is no longer < 0,
and the error handling in quota_write_inode() is incorrect,
fix these. This also fix a tune2fs segfault that currently
occurs when we add project and quota features to an inode
exhaustion ext4 filesystem.

Fixes: a701823a3150("libsupport: fix gcc -Wall nits")
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>