wic: Remove rpm and grabber dependencies from BaseImageCreator
BaseImageCreator is a base class for DirectImageCreator and others,
and imports rpm and grabber (which imports rpm).
The various plugins e.g. DirectPlugin import the creators and
therefore these dependencies, which manifest at run-time as e.g.:
Warning: Failed to load plugin imager/direct_plugin: No module named
rpm
(From OE-Core master rev:
a1e24c4a5f5771b7ad35e53ce96c6d82212e4d7e)
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
