Work around test-qht-par + gprof issues

Travis CI jobs are failing because of test-qht-par when gprof is
enabled.  Temporarily disable test-qht-par if gprof is enabled,
until we fix the bug.

# gpg: Signature made Fri 11 Jan 2019 18:23:29 GMT
# gpg:                using RSA key 2807936F984DC5A6
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>"
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/machine-next-pull-request:
  tests: Disable qht-bench parallel test when using gprof
  configure: Let the TARGET_GPROF var use the regular 'y' for Yes
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>