Check for e4fsprogs commands for ext4 support on RHEL/CentOS 5.x (#738706)

RHEL / CentOS 5.6 and later officially support ext4 file system [1].
From RHEL / CentOS 5.3 ext4 file system was included as a technology
preview.  Ext4 file system tools are in a separate package e4fsprogs,
using uniquely named commands.  The standard e2fsprogs commands only
support ext2 and ext3 file systems.

    # mkfs.ext4 /dev/sdb3
    # tune2fs -l /dev/sdb3
    tune2fs 1.39 (29-May-2006)
    tune2fs: Filesystem has unsupported feature(s) while trying to open /dev/sdb3
    Couldn't find valid filesystem superblock.
    # echo $?
    1
    # tune4fs -l /dev/sdb3
    tune4fs 1.41.12 (17-May-2010)
    Filesystem volume name:   <none>
    Last mounted on:          <not available>
    Filesystem UUID:          ba4a9d58-7728-4b47-8a90-80e772615637
    Filesystem magic number:  0xEF53
    Filesystem revision #:    1 (dynamic)
    Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
    ...

For ext4 only, search for the e4fsprogs specific commands first and the
standard e2fsprogs commands second.

[1] RHEL 5.6 Release Notes, 5. Filesystems and Storage
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/5.6_Release_Notes/ar01s05.html

Bug #738706 - GParted doesn't support ext4 on RHEL/CentOS 5.x