inet_dns: support TSIG (TO BE SQUASHED)

Tweak skip printouts to show the vital information
on the overview level of daily test results.

lib/kernel/test/inet_res_SUITE_data/run-ns

@@ -37,7 +37,8 @@
 ## * Terminate name server and wait for it.
 ##
 ## Prints status lines starting with tag and colon (think mail header):
-##   Error: have given up, no name server started
+##   Skip: have given up; no point in starting this name server
+##   Error: have given up; failed to start name server
 ##   Running: name server is running, waiting for "quit"
 ##   Other tags: diagnostics info
 #
@@ -84,9 +85,9 @@ test :"$3" != : || \
     error "Empty argument 3: Work/Zone subdir!"
 SRCDIR="`dirname "$ME"`/$3"
 test -d "$SRCDIR" || \
-    error "Missing zone directory $SRCDIR !"
+    error "Missing zone directory: $SRCDIR !"
 test -f "$SRCDIR/$INC_FILE" || \
-    error "Missing file: $SRCDIR/$INC_FILE !"
+    error "Missing include file: $SRCDIR/$INC_FILE !"
 DIR="$3"
 
 # Locate name server and check version.
@@ -96,17 +97,17 @@ do
 done
 
 NS_VER="`"$NS" -V 2>&1`" || \
-    skip "Name server ($NS) not found!"
+    skip "$NS: Not found!"
 NS_VER="`echo "$NS_VER" | head -1`"
 { echo "$NS_VER" |
       grep -q -e ' 2[.]9[.]' -e ' 2[.][1-9][0-9][0-9]*[.]' \
            -e ' [3-9][.]' -e ' [1-9][0-9][0-9]*[.]'
-} || skip "Name server $NS_VER < 2.9"
+} || skip "$NS_VER < 2.9"
 
 # Create working directory and cd to it
 mkdir "$DIR" >/dev/null 2>&1
 cd "$DIR" >/dev/null 2>&1 || \
-    error "Can not cd: $DIR !"
+    error "Cannot cd: $DIR !"
 DIR="$(pwd)"
 
 # Create $CONF_FILE