rc-service: print name of command on exec failure

[lanodan]

For example with noexec in the home, it changes:

$ rc-service -U foo start
 * rc-service: Permission denied

to:

$ rc-service -U foo start
 * rc-service: Failed executing '/home/haelwenn/.config/rc/init.d/foo': Permission denied

[navi-desu]

thanks!