Allow to specify storage policy when uploading objects

Client already supports -H/--header option when creating container
or uploading objects. This patch extends this option to support
Storage Policy.

e.g.,
    swift post con -H 'X-Storage-Policy:p1'
This creates one container 'con' with storage policy 'p1'.

    swift upload con obj -H 'X-Storage-Policy:p2'
This creates container 'con' with storage policy 'p2' and uploads
object 'obj' into it.

Also fixes segmented uploading to non-default storage policy container

When uploading large objects with segmentation to container with
non-default storage policy, there will be another 'xxx_segments'
container created, but with the default storage policy. This
results all the segments to be stored with the wrong policy.

This patch is for the Storage Policy feature, and also
compatible with old versions w/o Storage Policy support.

Change-Id: I5c19e90604a0bcf2c85e1732b8a0b97ae6801994
Merge "Allow to specify storage policy when uploading objects"
Fix context sensitive help for info and tempurl

Make it so that swift <cmd> --help will print the info
subcommand help for info and tempurl just like all the
other subcommands.

Also add unit tests to verify subcommand help.

Change-Id: Id3666dcf72a9727fbfda2f74c23293ada1c53aa0