main: Return D-Bus error on profile activation failure
Throw a D-Bus error when activating a profile fails:
gi.repository.GLib.GError: g-io-error-quark: GDBus.Error:org.gtk.GDBus.UnmappedGError.Quark._g_2dio_2derror_2dquark.Code26: Error writing '/sys/devices/system/cpu/cpufreq/policy1/energy_performance_preference': Device or resource busy (26)
Closes: #90 (closed)