Add log output of "x-openstack-request-id" from nova

This patch enables ceilometer to output
'x-openstack-request-id'/'x-compute-request-id'
of nova's responses to the log.
And it also enables ceilometer to output
request headers, request parameters,
other response headers and a response body to
the log when ceilometer calls nova.

DocImpact: There is a new configuration option
'nova_http_log_debug' in ceilometer.nova_client

Change-Id: Ic7e5301e46ac45597721f4a9b41c38f8c4ff0d14
Closes-bug: #1332060
Fix aggregator _get_unique_key method

This patch fixes the error that occurs in aggregator when project_id and
user_id are missing from aggregated sample. This problem appears for
example when swift incoming/outgoing bytes samples are aggregated and
non-authenticated users access swift publicly readable containers.

Change-Id: I8af201b6cf29b0206b3ffd996990f629d927334e
Closes-bug: #1333230
Fixes aggregator transformer timestamp and user input handling

Sample timestamps should be parsed with parse_isotime(), not
parse_strtime().

User input should be validated and fail with ValueError if wrong.

Closes-bug: #1342664
Change-Id: Ied429053eecfa355c1e73caae705e5b187c8b3aa
Merge "Add log output of "x-openstack-request-id" from nova"
Merge "Fix aggregator _get_unique_key method"
Merge "Fixes aggregator transformer timestamp and user input handling"