vty: Fix misusage of snprintf in vty/utils.c

Compiled with ubuntu 1204 (precise), where -Wformat-security is enabled by
-Wall.

Test yields ok, but the current implementation doesn't properly support
multi-character separators and end strings. So the test output is truncated.

Addresses:
utils.c: In function 'vty_cmd_string_from_valstr':
utils.c:84:2: warning: format not a string literal and no format arguments [-Wformat-security]
utils.c:84:2: warning: format not a string literal and no format arguments [-Wformat-security]
utils.c:108:2: warning: format not a string literal and no format arguments [-Wformat-security]
utils.c:108:2: warning: format not a string literal and no format arguments [-Wformat-security]
diff --git a/tests/Makefile.am b/tests/Makefile.am
index e5fc718..ecb2b6c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -5,7 +5,8 @@
                  conv/conv_test auth/milenage_test lapd/lapd_test	\
                  gsm0808/gsm0808_test gsm0408/gsm0408_test		\
 		 gb/bssgp_fc_test logging/logging_test fr/fr_test	\
-		 loggingrb/loggingrb_test strrb/strrb_test
+		 loggingrb/loggingrb_test strrb/strrb_test              \
+		 vty/vty_test
 
 if ENABLE_MSGFILE
 check_PROGRAMS += msgfile/msgfile_test
@@ -62,6 +63,9 @@
 strrb_strrb_test_SOURCES = strrb/strrb_test.c
 strrb_strrb_test_LDADD = $(top_builddir)/src/libosmocore.la
 
+vty_vty_test_SOURCES = vty/vty_test.c
+vty_vty_test_LDADD = $(top_builddir)/src/vty/libosmovty.la $(top_builddir)/src/libosmocore.la
+
 
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
@@ -91,7 +95,8 @@
              msgfile/msgfile_test.ok msgfile/msgconfig.cfg		\
              logging/logging_test.ok logging/logging_test.err		\
              fr/fr_test.ok loggingrb/logging_test.ok			\
-             loggingrb/logging_test.err	strrb/strrb_test.ok
+             loggingrb/logging_test.err	strrb/strrb_test.ok		\
+	     vty/vty_test.ok
 
 DISTCLEANFILES = atconfig