The initial hash serve loop exits in the case where interrupts are present
but probably checks a bit too often. Tweak that and also allow the slow
rehash loop to break on interrupt, improving bitbake Ctrl+C response.
(Bitbake rev: 4534365591fd17bcc2b684900863b67bc69519ae)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>