rgw/sse-s3: various improvements.

rgw/sse-s3: various improvements.

1. sse-s3 should not require bucketencryption policy, work w/ postobj
2. make bucket key name configurable
3. +rgw_remove_sse_s3_bucket_key

1. for sse-s3 should not require bucketencryption policy, work w/ postobj
get_crypt_attribute ->
using s->info.crypt_attribute_map instead of s->env to avoid havoing
	to know about HTTP_X_AMZ_SERVER_SIDE_ENCRYPTION_CUSTOMER_ALGORITHM names,
crypt_attribute_get -> crypt_attributes.get
	to consolidate crypt attribute sources
rework sse-s3 logic: sse-s3 can be specified entirely in the rest call,
	so remove requirement that bucket has bucket encryption policy.
	also avoid term "default encryption", prefer term "test key".

2. for make bucket key name configurable:
With this modification, sse-s3 key names default to being
the bucket id, but can be configured to instead consist
of the owners name, a fixed string, or variations thereof.

3. +rgw_remove_sse_s3_bucket_key
For sse-s3, keys are supposed to be managed entirely by s3.
This means when a bucket is removed, we should be removing its key,
which should no longer be in use for anything.  This is only safe
if the key was constructed using "%bucket_id", otherwise it might be
used in another bucket and we can never remove it automatically.

Signed-off-by: Marcus Watts <mwatts@redhat.com>
(cherry picked from commit 55daff7ae0aec48ea2210592ebcbaa2d8f397245)