update container image to use bci 15.6 as base image

package/Dockerfile

@@ -1,6 +1,6 @@
 # syntax=docker/dockerfile:1.7.0
 
-FROM registry.suse.com/bci/bci-base:15.5
+FROM registry.suse.com/bci/bci-base:15.6
 #awk is needed by sriov-manage utility from nvidia to perform gpu management
 
 RUN zypper -n install pciutils which curl ethtool awk