gluon-mesh-vpn-tunneldigger: only search for exactly the tunneldigger binary in watchdog (#1953)

(cherry picked from commit 68d970e9)

package/gluon-mesh-vpn-tunneldigger/luasrc/usr/bin/tunneldigger-watchdog

@@ -33,7 +33,7 @@ local function has_mesh_vpn_neighbours()
 end
 
 if uci:get_bool('tunneldigger', 'mesh_vpn', 'enabled') then
-	if io.popen('pgrep tunneldigger'):read('*l') ~= read_pid_file() then
+	if io.popen('pgrep -x /usr/bin/tunneldigger'):read('*l') ~= read_pid_file() then
 		os.execute('logger -t tunneldigger-watchdog "Process-Pid does not match with pid-File."')
 		restart_tunneldigger()
 		return