Improve shell_cmd error output when quiet=1.

When quiet is 1, the "Issuing:" line does not get printed.  So, when
an error occurs, the user has no idea what the failing command is.
With this change, the command_string contents will be included in the
error output.

Change-Id: I23813308397476eae8a70b2bd8c2c6af98e98030
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/gen_cmd.py b/lib/gen_cmd.py
index 81f64f0..52f255a 100644
--- a/lib/gen_cmd.py
+++ b/lib/gen_cmd.py
@@ -432,6 +432,8 @@
         if shell_rc in allowed_shell_rcs:
             break
         err_msg = "The prior shell command failed.\n"
+        if quiet:
+            err_msg += gp.sprint_var(command_string)
         if command_timed_out:
             err_msg += gp.sprint_var(command_timed_out)
             err_msg += gp.sprint_var(time_out)