Revert "MT#5155 use proper kernel for Guest Addition in case of 2+ kernels"

This reverts commit 3108fa4cff
I suspect here the root of the issue for MT#4605
(revert for now to finish with MT#5155).

deployment.sh

@@ -1216,7 +1216,7 @@ EOT
       echo "ngcp-mediaproxy-ng. kernel package already installed, skipping" | tee -a /tmp/dkms.log
     else
       # brrrr, don't tell this anyone or i'll commit with http://whatthecommit.com/ as commit msg!
-      KERNELHEADERS=$(basename $(ls -d ${TARGET}/usr/src/linux-headers*amd64 | sort -u | tail -1))
+      KERNELHEADERS=$(basename $(ls -d ${TARGET}/usr/src/linux-headers*amd64 | sort -u | head -1))
       if [ -z "$KERNELHEADERS" ] ; then
         die "Error: no kernel headers found for building the ngcp-mediaproxy-ng kernel module."
       fi