Fix capture method comparison

If the default is "termshark", then termshark's dual-pronged
dumpcap-then-tshark capture method is used. But it's misleading to print
out that when termshark's capture failed, here is the stderr from the
failing capture program, "termshark". So I swap it out for some other
language in the default case. This compares the binaries properly, via
their full paths - if termshark is started as e.g. ./termshark, my
comparison failed.

cmd/termshark/termshark.go

@@ -738,8 +738,9 @@ func cmain() int {
 				// variable set that causes it to try dumpcap, then tshark, in that order (for
 				// efficiency of capture, but falling back to tshark for extcap interfaces).
 				// But telling the user the capture process is "termshark" is misleading.
-				cbin := termshark.CaptureBin()
-				if cbin == "termshark" {
+				cbin, err1 := filepath.Abs(filepath.FromSlash(termshark.CaptureBin()))
+				def, err2 := filepath.Abs("termshark")
+				if err1 == nil && err2 == nil && cbin == def {
 					cbin = "the capture process"
 				}