src/pmdas/linux/proc_net_dev.c: fix scanf format for /proc/net/if_inet6
src/pmdas/linux/proc_net_dev.c: fix scanf format for /proc/net/if_inet6

We were assuming %02x for the 4 fields between the ipv6 addr and
the interface name, as in:
fe80000000000000505400fffe9270ac 02 40 20 80     ens7
                                 ^^ ^^ ^^ ^^
but on bozo, we have these lines:
fe80000000000000fc5400fffe906c44 20e 40 20 80    vnet9
                                 ^^^
fe80000000000000fc5400fffe199ad0 127 40 20 80    vnet8
                                 ^^^
so use %x instead of %02x, and drop the 20 len from the next %s
at the same time.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp