Fix failure to recognise whole disk file systems in certain cases (#743181)

When the following conditions were met GParted would fail to recognise a
newly created whole disk device file system, and instead show an unknown
file system filling the disk:

1) Disk was previously partitioned and contained at least one partition.

2) Using libparted version 2.0 to 3.0 inclusive.

Initial status:
    # blkid | fgrep sdc
    # fgrep sdc /proc/partitions
       8       32  976762584 sdc
       8       33  104857600 sdc1
    # parted /dev/sdc
    GNU Parted 2.4
    Using /dev/sdc
    Welcome to GNU Parted! Type 'help' to view a list of commands.
    (parted) print
    Model: ATA ST1000LM024 HN-M (scsi)
    Disk /dev/sdc: 1000GB
    Sector size (logical/physical): 512B/4096B
    Partition Table: msdos

    Number  Start   End    Size   Type     File system  Flags
     1      1049kB  107GB  107GB  primary

When creating the loop partition table libparted would not inform the
kernel to delete the old partitions.  /proc/partitions still contained
the details of the old partitions.
    (parted) mktable loop
    Warning: The existing disk label on /dev/sdc will be destroyed and
    all data on this disk will be lost. Do you want to continue?
    Yes/No? Yes
    (parted) print
    Model: ATA ST1000LM024 HN-M (scsi)
    Disk /dev/sdc: 1000GB
    Sector size (logical/physical): 512B/4096B
    Partition Table: loop

    Number  Start  End  Size  File system  Flags

    (parted) quit
    # fgrep sdc /proc/partitions
       8       32  976762584 sdc
       8       33  104857600 sdc1

Creation of the whole disk device file system goes unnoticed by blkid
because the kernel and therefore blkid's cache have stale partition
information.
    # mkfs.xfs -f /dev/sdc
    # blkid | fgrep sdc

NOTE:
On a Linux Software RAID array, as opposed to a hard disk, blkid does
notice creation of the whole disk device file system.  However the
kernel still has old partition details.

This was fixed in libparted 3.1 by commit:

    http://git.savannah.gnu.org/cgit/parted.git/commit/?id=f5c909c0cd50ed52a48dae6d35907dc08b137e88
    libparted: remove has_partitions check to allow loopback partitions

Fix by deleting old partitions before creating the loop table when
compiled with a broken version of libparted.  The GParted UI provides
no feedback while a new partition table is created, and with some
versions of GTK the UI become unresponsive too, so it is important to be
as fast as possible.  Evaluated three different methods, deleting 15 and
22 MSDOS partitions on a physical 5400 RPM hard drive using libparted
2.4:

M1) Delete and commit one partition at a time.
    Takes up to 24 seconds to delete 15 partitions.  With 22 partitions
    libparted always reports finding some of the partitions busy and
    unable to inform the kernel about the modifications.
    Too slow and doesn't work.

M2) Delete all partitions in one go and commit once.
    Takes up to 1.4 seconds to delete either 15 or 22 partitions.  Never
    removes partitions 17 and higher from the kernel.
    Doesn't work.

M3) Write GPT table (letting libparted delete any old partitions).
    Takes up to 0.8 seconds to delete either 15 or 22 partitions.
    Fast and works.

Use method 3 - write a GPT table thus using libparted code to inform the
kernel of the old partition deletions.

Bug 743181 - Add unpartitioned drive read-write support