block: introducing 'bdrv_co_delete_file' interface

block: introducing 'bdrv_co_delete_file' interface

Adding to Block Drivers the capability of being able to clean up
its created files can be useful in certain situations. For the
LUKS driver, for instance, a failure in one of its authentication
steps can leave files in the host that weren't there before.

This patch adds the 'bdrv_co_delete_file' interface to block
drivers and add it to the 'file' driver in file-posix.c. The
implementation is given by 'raw_co_delete_file'.

Suggested-by: Daniel P. Berrangé <[email protected]>
Signed-off-by: Daniel Henrique Barboza <[email protected]>
Message-Id: <20200130213907.2830642[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>