vty: Makefile: Fix LIBVERSION typo introduced in 0.12.0 release

Setting age to 5 is cleary an error, it should be increment by one
instead as APIs were added 0.11->0.12 and none modified or removed.

Change-Id: I3b3bc808349bc2f949ef9eef64f39e7202ddf946
diff --git a/src/vty/Makefile.am b/src/vty/Makefile.am
index 5d0ded7..49813c5 100644
--- a/src/vty/Makefile.am
+++ b/src/vty/Makefile.am
@@ -1,7 +1,7 @@
 # This is _NOT_ the library release version, it's an API version.
 # Please read chapter "Library interface versions" of the libtool documentation
 # before making any modifications: https://www.gnu.org/software/libtool/manual/html_node/Versioning.html
-LIBVERSION=5:0:5
+LIBVERSION=5:0:1
 
 AM_CPPFLAGS = -I$(top_srcdir)/include -I$(top_builddir)/include
 AM_CFLAGS = -Wall $(TALLOC_CFLAGS)