oeqa/buildperf: Add 'bitbake -m' on sync function to ensure bitbake is unloaded
Add 'bitbake -m' to the sync method and ensure all process related to
bitbake are correctly unloaded before doing the different measurements.
Also add a call to sync funtion on Test4 before final measurment of
eSDK deploy dir disk usage.
Signed-off-by: Jose Perez Carranza <jose.perez.carranza@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
