xfs_quota: add support for passing project paths on cmdline

xfs_quota: add support for passing project paths on cmdline

/etc/project is currently required for using project quota. This
patch adds ability to specify paths at command line.

fs_table_insert_project_path() introduced in libxcmd. Allows to insert
arbitrary path to fs_* iterating engine. We insert our paths with
-1 as project id (because we know no "original" id for this path
and generally this knowledge is not needed).

New option introduced for paths passing - project -p <path>.

Example:
$ sudo rm -f /etc/projects /etc/projid

$ sudo ./xfs_quota -x -c "project -p /tmp/xx -s 60"
Setting up project 60 (path /tmp/xx)...
Processed 1 (/etc/projects and cmdline) paths for project 60 with
recursion depth infinite (-1).

$ sudo ./xfs_quota -x -c "project -p /tmp/xx -c 60"
Checking project 60 (path /tmp/xx)...
Processed 1 (/etc/projects and cmdline) paths for project 60 with
recursion depth infinite (-1).

$ sudo ./xfs_quota -x -c "project -p /tmp/xx -c 70"
Checking project 70 (path /tmp/xx)...
/tmp/xx - project identifier is not set (inode=60, tree=70)
/tmp/xx/file1 - project identifier is not set (inode=60, tree=70)
/tmp/xx/file2 - project identifier is not set (inode=60, tree=70)
/tmp/xx/file3 - project identifier is not set (inode=60, tree=70)
/tmp/xx/dir1 - project identifier is not set (inode=60, tree=70)
/tmp/xx/dir2 - project identifier is not set (inode=60, tree=70)
Processed 1 (/etc/projects and cmdline) paths for project 70 with
recursion depth infinite (-1).

$ sudo ./xfs_quota -x -c "project -p /tmp/xx -s 70"
Setting up project 70 (path /tmp/xx)...
Processed 1 (/etc/projects and cmdline) paths for project 70 with
recursion depth infinite (-1).

$ sudo ./xfs_quota -x -c "project -p /tmp/xx -c 70"
Checking project 70 (path /tmp/xx)...
Processed 1 (/etc/projects and cmdline) paths for project 70 with
recursion depth infinite (-1).

Signed-off-by: Arkadiusz Miśkiewicz <arekm@maven.pl>
Reviewed-by: Donald Douwsma <ddouwsma@bigpond.net.au>
Reviewed-by: Christoph Hellwig <hch@lst.de>