gnetworkmonitornetlink.c: Make the error messages less geeky
gnetworkmonitornetlink.c: Make the error messages less geeky

This makes several different errors have identical messages, but
they're pretty much "can't happen" situations anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=664406

lukasz-skalski/glib,01org/android-bluez-glib,tchakabam/glib,pstglia/external-bluetooth-glib,lukasz-skalski/glib,01org/android-bluez-glib,pstglia/external-bluetooth-glib,cosimoc/glib,endlessm/glib,bluez-android/glib,johne53/MB3Glib,pstglia/external-bluetooth-glib,johne53/MB3Glib,antono/glib,tamaskenez/glib,gale320/glib,tchakabam/glib,ieei/glib,iConsole/Console-OS_external_bluetooth_glib,cosimoc/glib,pstglia/platform-external-bluetooth-glib,pstglia/external-bluetooth-glib,01org/android-bluez-glib,darren-clark/android_platform_external_bluetooth_glib,djdeath/glib,lukasz-skalski/glib,gale320/glib,endlessm/glib,bluez-android/glib,bluez-android/glib,justinkb/aosp-bluez.glib,01org/android-bluez-glib,gale320/glib,tamaskenez/glib,johne53/MB3Glib,mzabaluev/glib,mzabaluev/glib,darren-clark/android_platform_external_bluetooth_glib,cention-sany/glib,iConsole/Console-OS_external_bluetooth_glib,tamaskenez/glib,gale320/glib,cosimoc/glib,Distrotech/glib,darren-clark/android_platform_external_bluetooth_glib,tamaskenez/glib,djdeath/glib,ieei/glib,tchakabam/glib,MathieuDuponchelle/glib,justinkb/aosp-bluez.glib,darren-clark/android_platform_external_bluetooth_glib,MathieuDuponchelle/glib,bluez-android/glib,krichter722/glib,cosimoc/glib,justinkb/aosp-bluez.glib,justinkb/aosp-bluez.glib,cention-sany/glib,lukasz-skalski/glib,ieei/glib,pstglia/platform-external-bluetooth-glib,lukasz-skalski/glib,krichter722/glib,pstglia/platform-external-bluetooth-glib,endlessm/glib,Distrotech/glib,cention-sany/glib,pstglia/platform-external-bluetooth-glib,mzabaluev/glib,pstglia/platform-external-bluetooth-glib,iConsole/Console-OS_external_bluetooth_glib,djdeath/glib,tamaskenez/glib,justinkb/aosp-bluez.glib,MathieuDuponchelle/glib,johne53/MB3Glib,krichter722/glib,krichter722/glib,tchakabam/glib,endlessm/glib,iConsole/Console-OS_external_bluetooth_glib,iConsole/Console-OS_external_bluetooth_glib,cosimoc/glib,01org/android-bluez-glib,darren-clark/android_platform_external_bluetooth_glib,antono/glib,ieei/glib,mzabaluev/glib,antono/glib,cention-sany/glib,MathieuDuponchelle/glib,Distrotech/glib,endlessm/glib,mzabaluev/glib,tchakabam/glib,gale320/glib,MathieuDuponchelle/glib,johne53/MB3Glib,johne53/MB3Glib,bluez-android/glib,djdeath/glib,cention-sany/glib,Distrotech/glib,djdeath/glib,pstglia/external-bluetooth-glib,ieei/glib,krichter722/glib,antono/glib,Distrotech/glib