fmf: Use one fewer than number of available CPUs again

This effectively reverts b8582198ca
as I can not get the testing farm bare metal machines working
downstream and even if I managed to, without also using the testing
farm bare metal machines upstream (for which there is no capacity),
the setup would very quickly bitrot anyway so we'll just run the
container based tests for now.

test/fmf/integration-tests/test.sh

@@ -112,13 +112,6 @@ if [[ ! -e /dev/kvm ]]; then
     export TEST_NO_QEMU=1
 fi
 
-NPROC=$(nproc)
-if [[ $NPROC -ge 10 ]]; then
-    NPROC=$((NPROC / 2))
-else
-    NPROC=$((NPROC - 1))
-fi
-
 # Create missing mountpoint for mkosi sandbox.
 mkdir -p /etc/pacman.d/gnupg
 
@@ -134,7 +127,7 @@ mkosi -f sandbox \
     --suite integration-tests \
     --print-errorlogs \
     --no-stdsplit \
-    --num-processes "$NPROC" && EC=0 || EC=$?
+    --num-processes "$(($(nproc) - 1))" && EC=0 || EC=$?
 
 find build/meson-logs -type f -exec mv {} "$TMT_TEST_DATA" \;
 find build/test/journal -type f -exec mv {} "$TMT_TEST_DATA" \;