btrfs-progs: error if device have no space to make primary chunks

btrfs-progs: error if device have no space to make primary chunks

The previous patch works fine if the size of specified volume to mkfs
is less than 4MB. However usually btrfs requires more than 4MB to work,
and the minimum preferred size is depending on the raid setting etc.

This patch let mkfs print error message if it cannot allocate one of
chunks should be there at first.

 [before]
  # truncate --size=4500K testfile
  # ./mkfs.btrfs -f testfile
   :
  SMALL VOLUME: forcing mixed metadata/data groups
  mkfs.btrfs: mkfs.c:84: make_root_dir: Assertion `!(ret)' failed.
  Aborted (core dumped)

 [After]
  # truncate --size=4500K testfile
  # ./mkfs.btrfs -f testfile
   :
  SMALL VOLUME: forcing mixed metadata/data groups
  no space to alloc data/metadata chunk
  failed to setup the root directory

TBD is calculate minimum size for setting and put it in the error
message to let user know how large amount of volume is required.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>