libvirt.spec: Build & run tests in parallel

So far, the main code is built in parallel, which makes it pretty
fast. But with a lots of tests we have now I've noticed this part
takes too much time to build. The problem was that tests were
build and run in a single job.

Also, 'make' in the first hunk is useless. The test suite is not
built due to 'make all' because there's no .git in the sources
unpacked from a tar.xz archive. It's 'make check' which triggers
tests build.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

libvirt.spec.in

@@ -1290,7 +1290,6 @@ rm -fr %{buildroot}
 
 %check
 cd tests
-make
 # These tests don't current work in a mock build root
 for i in nodeinfotest seclabeltest
 do
@@ -1299,7 +1298,7 @@ do
   printf '#!/bin/sh\nexit 0\n' > $i
   chmod +x $i
 done
-if ! make check VIR_TEST_DEBUG=1
+if ! make %{?_smp_mflags} check VIR_TEST_DEBUG=1
 then
   cat test-suite.log || true
   exit 1