bitbake: build: make shell traps less chatty when 'bitbake -v' is used

This shuts up both the DEBUG and EXIT handlers.

Also, remove an unneeded "set -o errtrace" (i.e. set -E),
since we no longer use an ERR trap.

(Bitbake rev: 89e851fa0403d1e98aeed69990101e3f84f0b283)

Signed-off-by: Chris Laplante <chris.laplante@agilent.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>