misc: clean up "pcap [rx|tx] trace" debug CLI

Separate debug CLI arg parsing from the underlying action
function. Fixes a number of subtle ordering dependencies, and will
allow us to add a binary API to control the feature at some point in
the future.

Type: refactor
Ticket: VPP-1770

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: Id0dbeda06dad20e756c941c691e2088ce3c50ec7

extras/pcapcli/setup.pcapcli

@@ -0,0 +1,34 @@
+set term pag off
+loop create
+loop create
+set int ip address loop0 192.168.1.1/24
+set int state loop0 up
+
+set int ip address loop1 192.168.2.1/24
+set int state loop1 up
+
+packet-generator new {
+    name pg0
+    limit 1
+    size 300-300
+    interface loop0
+    node ethernet-input
+    data { IP4: 1.2.3 -> 4.5.6
+           UDP: 192.168.1.10 -> 192.168.2.10
+           UDP: 1234 -> 2345
+           incrementing 286
+    }
+}
+
+packet-generator new {
+    name pg1
+    limit 1
+    size 300-300
+    interface loop1
+    node ethernet-input
+    data { IP4: 1.2.3 -> 4.5.6
+           UDP: 192.168.2.10 -> 192.168.1.10
+           UDP: 1234 -> 2345
+           incrementing 286
+    }
+}