fix(tftf): Prevent UART from exiting early

Ensured all calls to exit_uart in 'expect' wait for the string
"Exiting tests." to prevent the uart from being closed before all of the
test result information has been written.

Signed-off-by: Nathan Dunne <Nathan.Dunne@arm.com>
Change-Id: I4793be8fd5a2bbf3e2a3a72e14b0d702d52e05e4
diff --git a/expect/tftf.exp b/expect/tftf.exp
index bcc04fc..87a5f33 100644
--- a/expect/tftf.exp
+++ b/expect/tftf.exp
@@ -19,11 +19,11 @@
 		exit_uart 0
 	}
 	"Tests Passed  : 0" {
-		puts "<<TFTF no tests passed>>"
+		expect_string "Exiting tests." "<<TFTF no tests passed>>"
 		exit_uart -1
 	}
 	-re "Tests Failed  : \[^0]" {
-		puts "<<TFTF Fail>>"
+		expect_string "Exiting tests." "<<TFTF Fail>>"
 		exit_uart -1
 	}
 	timeout {