validate server action 'console_output' attributes

This patch adds the JSON schema for Nova V2 & V3 get_console_output
server action APIs response and validate the response with added
JSON schema to block the backward incompatibility change in the future.

The response body of get_console_output V2 & V3 APIs is same and given
below:

{
        "output": "FAKE CONSOLE OUTPUT\nANOTHER\nLAST LINE"
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I22e61d1fed926aa9a310a46b12748db401dec045
log request start when tracing classes

When tracing rest calls for debugging purposes, logging the start
of the request is also extremely helpful, as it makes it possible
to discover that the key issue is glance is in a hung state and
not responding to any requests.

Prereq for blueprint:javelin2

Change-Id: I9aca99119fc1569c78788b11a8a32d72eaecd0a1
allow 'main' as valid name for find_test_caller

find_test_caller assumed that the rest clients were only ever run
under testr. With the introduction of javelin into the tempest
tree this will not be true. 'main' is a completely valid name
for well formed programs, so make that an option as well.

Prereq for blueprint:javelin2

Change-Id: I9a591eaa1cf4dabba58f06a64814611a05a51365
allow for arbitrary kwargs in image client

in order to upload 3 part images with our glance client you need
to allow for passing arbitrary metadata to the image (ramdisk_id
and kernel_id). Remove our kwargs filter to let that happen.

Prereq of blueprint:javelin2

Change-Id: Idff078a2a225a6531b6ce0cf49cb03cc75618e32
Merge "log request start when tracing classes"
Merge "validate server action 'console_output' attributes"
Merge "allow 'main' as valid name for find_test_caller"
Merge "allow for arbitrary kwargs in image client"