mkfs.nilfs2: fix gcc warning "array subscript is above array bounds"

Recent gcc compiler (e.g. gcc version 4.9.1) gives a false positive
warning during the build of mkfs.nilfs2:

 mkfs.c: In function 'main':
 mkfs.c:540:47: warning: array subscript is above array bounds [-Warray-bounds]
    struct nilfs_segment_info *si = &di->seginfo[i];
                                               ^
 mkfs.c:540:47: warning: array subscript is above array bounds [-Warray-bounds]
 mkfs.c:540:47: warning: array subscript is above array bounds [-Warray-bounds]
 mkfs.c:540:47: warning: array subscript is above array bounds [-Warray-bounds]

This fixes the issue.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
nilfs_cleanerd.conf: set min_reclaimable_blocks parameter to 10 percent

Increase the default value of min_reclaimable_blocks parameter to 10
percent from the original 5 percent for the following reasons:

 1) In real environment, the 10 percent threshold looks better than 5
    percent to reduce relocation of static data.  The ratio of live
    blocks in a lump of static data region is typically about 90-99
    percent according to the result of "lssu -l".

 2) When we set min_reclaimable_blocks to 10 percent, 10 percent of
    disk space (excluding 5 percent reserved capacity) will remain
    unreclaimed at worst.  But, this is acceptable because the default
    value of min_clean_segments is 10 percent and
    mc_min_reclaimable_blocks (1%) is applied while the ratio of free
    space is below 10 percent.

Cc: Andreas Rohner <andreas.rohner@gmx.net>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
bin/*: improve error message on failure of nilfs_open()

The error message on failure of nilfs_open() function has two issues
in commands lscp, lssu, mkcp, chcp, rmcp, and dumpseg:

 1) When device name is omitted, a null pointer is passed to a string
    type field of the error message and a broken message is printed as
    below:

      lssu: (null): cannot open NILFS

 2) Description of errno is not shown in the error message.

This fixes these issues.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
libnilfs: set errno when device doesn't contain valid NILFS data

Fix the bug that no error number is set to errno variable if the
specified device doesn't contain a valid nilfs file system, which
causes caller programs to output successful message wrongly.  Three
functions, nilfs_open(), nilfs_sb_read() and nilfs_sb_write() have
this flaw.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
nilfs-utils: v2.2.1 release

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>