Make NPM tests runnable by root

The tests can now be run as root. This is most likely required in some
cases and it should not break things if they are run as root (e.g. inside
a VM with no other users).

NPM prevents the use of the root user (due to modules getting root access)
and uses an unprivileged user to install the modules. As maxctrl has to
generate the version information at install time, running `npm install` as
root will fail due to missing privileges to the current working
directory. To work around this, an explicit step was added.

Also changed the maxadmin checks to maxctrl to remove the dependency on
the socket file location being writable by non-root users
(/var/run/maxscale/ might not be accessible to all users).

test/stop_maxscale.sh

@@ -8,10 +8,10 @@ maxscaledir=$MAXSCALE_DIR
 
 test -z "$MAXSCALE_DIR" && exit 1
 
-for ((i=0;i<20;i++))
+for ((i=0;i<200;i++))
 do
     pkill '^maxscale$' || break
-    sleep 0.5
+    sleep 0.1
 done
 
 # If it wasn't dead before, now it is