oeqa/testsdk: Use original PATH
We want to test the SDK with PATH from the original host, not with our own
tools injected via HOSTTOOLS. It even uses some tools which aren't in
HOSTTOOLS.
This is necessary after changing the SDK to not reset PATH to the system
default which is bad for other reasons and brings the testing into sync
with that change.
(From OE-Core rev:
87c9602fd0dedc7bcf75b822aaf5f6ebfc17737c)
(From OE-Core rev:
de3f405b6cf96311ced86bccf7202370e4d1481a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
