build: install into bin instead of sbin

Installs into bin instead of sbin per guidelines.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Ie3fd4aa21c2644b2673f80a17dee13819b6b546e
diff --git a/Makefile.am b/Makefile.am
index b138aea..7c7271e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,4 +1,4 @@
-sbin_PROGRAMS = phosphor-user-manager
+bin_PROGRAMS = phosphor-user-manager
 
 noinst_HEADERS = user_mgr.hpp users.hpp