We previously put a sync call into devtool to try and combat the bitbake
timeout issues on the autobuilder. It isn't enough as the timeouts occur
mid test. They are also occurring on non-devtool tests.
Add in sync calls around command execution instead.
(From OE-Core rev: ceca5ed121e2b54415a7ab3a217882e4ea86923a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>