test: Make handling of shell prompts with escapes a little more reliable

When using the old-style "pane" methods of executing commands during the
tests, we need to scan the shell output for prompts in order to tell when
commands have finished.  This is inherently unreliable because commands
could output things that look like prompts, and prompts might not look like
we expect them to.  The only way to really fix this is to use a better way
of dispatching commands, like the newer "context" system.

However, it's awkward to convert everything to "context" right at the
moment, so we're still relying on some tests that do work most of the time.
It is, however, particularly sensitive to fancy coloured prompts using
escape sequences.  Currently we try to handle this by stripping actual
ESC characters with tr, then looking for some common variants.

We can do a bit better: instead strip all escape sequences using sed before
looking for our prompt.  Or, at least, any one using [a-zA-Z] as the
terminating character. Strictly speaking ANSI escapes can be terminated by
any character in 0x40..0x7e, which isn't easily expressed in a regexp.
This should capture all common ones, though.

With this transformation we can simplify the list of patterns we then look
for as a prompt, removing some redundant variants.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

test/lib/term

@@ -203,11 +203,9 @@ pane_wait() {
 
 	__done=0
 	while
-		__l="$(tail -1 ${LOGDIR}/pane_${__lc}.log | tr -d [:cntrl:])"
+		__l="$(tail -1 ${LOGDIR}/pane_${__lc}.log | sed 's/[[][^a-zA-Z]*[a-zA-Z]//g')"
 		case ${__l} in
-		'$ ' | '# ' | '# # ' | *"$ " | *"# ") return ;;
+		*"$ " | *"# ") return ;;
-		*" #[m " | *" #[m [K" | *"]# ["*) return ;;
-		*' $ [6n' | *' # [6n' ) return ;;
 		esac
 	do sleep 0.1 || sleep 1; done
 }