Change names of tcptuning classes.

As it turns out, each name part for a class name has to begin with
a lowercase letter in later puppet versions. Make it so.

manifests/tcptuning/10g.pp → manifests/tcptuning/if10g.pp

-class networking::tcptuning::10g
+class networking::tcptuning::if10g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().

manifests/tcptuning/1g.pp → manifests/tcptuning/if1g.pp

-class networking::tcptuning::1g
+class networking::tcptuning::if1g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().

manifests/tcptuning/40g.pp → manifests/tcptuning/if40g.pp

-class networking::tcptuning::40g
+class networking::tcptuning::if40g
 {
     sysctl {
 	# Increase TCP max buffer size settable using setsockopt().