Use uwsgi binary from path

All these uwsgi invocations assume that the uwsgi binary is in the
same directory as their project binaries are installed into (probably
/usr/bin).  That may not be correct -- for example if using a packaged
uwsgi on Fedora the binary will live in /usr/sbin/uwsgi (not /usr/bin
where the project files from pip are).

Switch invocations to just find it in the path.

Change-Id: I298e3374e9c84e209ffcabbaaacda17f8df19f4f
diff --git a/lib/glance b/lib/glance
index 9398bd2..8ee422d 100644
--- a/lib/glance
+++ b/lib/glance
@@ -392,7 +392,7 @@
 
     run_process g-reg "$GLANCE_BIN_DIR/glance-registry --config-file=$GLANCE_CONF_DIR/glance-registry.conf"
     if [[ "$WSGI_MODE" == "uwsgi" ]]; then
-        run_process g-api "$GLANCE_BIN_DIR/uwsgi --procname-prefix glance-api --ini $GLANCE_UWSGI_CONF"
+        run_process g-api "$(which uwsgi) --procname-prefix glance-api --ini $GLANCE_UWSGI_CONF"
     else
         run_process g-api "$GLANCE_BIN_DIR/glance-api --config-dir=$GLANCE_CONF_DIR"
     fi