virt.tests: autotest.cpuflags test fix

Add control file to shared.control and update compress command to
compress virt dir to source tarball because autotest.cpuflags test
requried it;
Update compress result command to ignore core dump and crash file to
avoid compress or scp failed;

Signed-off-by: Xu Tian <xutian@redhat.com>
Merge pull request #934 from xutian/fix_autotest_cpuflags_stress

virt.tests: autotest.cpuflags test fix