posix: sockets: address was not set in recvfrom
posix: sockets: address was not set in recvfrom

The address is an optional parameter of recvfrom. If it is
not null, recvfrom must store the address of the sender.
However this was only allowed if res was equal to 0, which
is wrong since res contains the number of bytes received
or -1.
This commit ensures that the address is set only if no
previous errors happened before.

Signed-off-by: Francois Berder <0eabc3e9da54407da074ac08d4217d54f5b94915@imgtec.com>

neiljay/RIOT,jbeyerstedt/RIOT-OTA-update,A-Paul/RIOT,aeneby/RIOT,rfuentess/RIOT,kYc0o/RIOT,jasonatran/RIOT,smlng/RIOT,Ell-i/RIOT,avmelnikoff/RIOT,kbumsik/RIOT,BytesGalore/RIOT,rfuentess/RIOT,jasonatran/RIOT,ks156/RIOT,adrianghc/RIOT,ks156/RIOT,neiljay/RIOT,roberthartung/RIOT,beurdouche/RIOT,mtausig/RIOT,beurdouche/RIOT,yogo1212/RIOT,ks156/RIOT,neumodisch/RIOT,A-Paul/RIOT,LudwigKnuepfer/RIOT,neiljay/RIOT,kaleb-himes/RIOT,TobiasFredersdorf/RIOT,dailab/RIOT,avmelnikoff/RIOT,LudwigOrtmann/RIOT,Josar/RIOT,syin2/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,beurdouche/RIOT,plushvoxel/RIOT,immesys/RiSyn,LudwigKnuepfer/RIOT,kbumsik/RIOT,avmelnikoff/RIOT,aeneby/RIOT,RIOT-OS/RIOT,Josar/RIOT,jasonatran/RIOT,adjih/RIOT,dailab/RIOT,kaleb-himes/RIOT,aeneby/RIOT,kYc0o/RIOT,Ell-i/RIOT,hamilton-mote/RIOT-OS,LudwigKnuepfer/RIOT,gebart/RIOT,immesys/RiSyn,lazytech-org/RIOT,kaspar030/RIOT,Ell-i/RIOT,jfischer-phytec-iot/RIOT,thomaseichinger/RIOT,x3ro/RIOT,beurdouche/RIOT,yogo1212/RIOT,dailab/RIOT,LudwigOrtmann/RIOT,kaleb-himes/RIOT,immesys/RiSyn,biboc/RIOT,RIOT-OS/RIOT,immesys/RiSyn,kYc0o/RIOT,neiljay/RIOT,x3ro/RIOT,Josar/RIOT,jbeyerstedt/RIOT-OTA-update,kaleb-himes/RIOT,OlegHahm/RIOT,Hyungsin/RIOT-OS,foss-for-synopsys-dwc-arc-processors/RIOT,plushvoxel/RIOT,toonst/RIOT,BytesGalore/RIOT,kbumsik/RIOT,A-Paul/RIOT,hamilton-mote/RIOT-OS,foss-for-synopsys-dwc-arc-processors/RIOT,Hyungsin/RIOT-OS,adrianghc/RIOT,Josar/RIOT,neumodisch/RIOT,neumodisch/RIOT,josephnoir/RIOT,TobiasFredersdorf/RIOT,kbumsik/RIOT,authmillenon/RIOT,cladmi/RIOT,lazytech-org/RIOT,RIOT-OS/RIOT,authmillenon/RIOT,neumodisch/RIOT,syin2/RIOT,aeneby/RIOT,dkm/RIOT,adjih/RIOT,dailab/RIOT,gautric/RIOT,Hyungsin/RIOT-OS,kYc0o/RIOT,OlegHahm/RIOT,LudwigOrtmann/RIOT,OlegHahm/RIOT,dailab/RIOT,aeneby/RIOT,josephnoir/RIOT,roberthartung/RIOT,Ell-i/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,x3ro/RIOT,Hyungsin/RIOT-OS,BytesGalore/RIOT,biboc/RIOT,lazytech-org/RIOT,ant9000/RIOT,kaspar030/RIOT,thomaseichinger/RIOT,adrianghc/RIOT,jfischer-phytec-iot/RIOT,OTAkeys/RIOT,BytesGalore/RIOT,dkm/RIOT,ant9000/RIOT,jbeyerstedt/RIOT-OTA-update,Hyungsin/RIOT-OS,basilfx/RIOT,OlegHahm/RIOT,kaleb-himes/RIOT,rfuentess/RIOT,basilfx/RIOT,gebart/RIOT,kerneltask/RIOT,lazytech-org/RIOT,jbeyerstedt/RIOT-OTA-update,kerneltask/RIOT,roberthartung/RIOT,beurdouche/RIOT,josephnoir/RIOT,jasonatran/RIOT,x3ro/RIOT,hamilton-mote/RIOT-OS,foss-for-synopsys-dwc-arc-processors/RIOT,thomaseichinger/RIOT,gebart/RIOT,josephnoir/RIOT,authmillenon/RIOT,biboc/RIOT,BytesGalore/RIOT,toonst/RIOT,toonst/RIOT,TobiasFredersdorf/RIOT,neumodisch/RIOT,kbumsik/RIOT,cladmi/RIOT,mfrey/RIOT,jfischer-phytec-iot/RIOT,Josar/RIOT,hamilton-mote/RIOT-OS,jasonatran/RIOT,TobiasFredersdorf/RIOT,miri64/RIOT,A-Paul/RIOT,avmelnikoff/RIOT,roberthartung/RIOT,ks156/RIOT,adrianghc/RIOT,A-Paul/RIOT,plushvoxel/RIOT,LudwigOrtmann/RIOT,roberthartung/RIOT,mfrey/RIOT,biboc/RIOT,adjih/RIOT,rfuentess/RIOT,basilfx/RIOT,mtausig/RIOT,ks156/RIOT,syin2/RIOT,adrianghc/RIOT,mfrey/RIOT,immesys/RiSyn,gautric/RIOT,OTAkeys/RIOT,basilfx/RIOT,smlng/RIOT,hamilton-mote/RIOT-OS,syin2/RIOT,rfuentess/RIOT,plushvoxel/RIOT,miri64/RIOT,toonst/RIOT,jfischer-phytec-iot/RIOT,authmillenon/RIOT,LudwigKnuepfer/RIOT,gautric/RIOT,yogo1212/RIOT,kaspar030/RIOT,miri64/RIOT,kerneltask/RIOT,miri64/RIOT,lazytech-org/RIOT,dkm/RIOT,adjih/RIOT,gautric/RIOT,cladmi/RIOT,TobiasFredersdorf/RIOT,ant9000/RIOT,smlng/RIOT,mfrey/RIOT,mtausig/RIOT,OlegHahm/RIOT,yogo1212/RIOT,yogo1212/RIOT,josephnoir/RIOT,smlng/RIOT,avmelnikoff/RIOT,kYc0o/RIOT,thomaseichinger/RIOT,miri64/RIOT,yogo1212/RIOT,kerneltask/RIOT,adjih/RIOT,gautric/RIOT,cladmi/RIOT,authmillenon/RIOT,immesys/RiSyn,neumodisch/RIOT,dkm/RIOT,OTAkeys/RIOT,OTAkeys/RIOT,kaspar030/RIOT,dkm/RIOT,RIOT-OS/RIOT,jfischer-phytec-iot/RIOT,cladmi/RIOT,basilfx/RIOT,LudwigOrtmann/RIOT,RIOT-OS/RIOT,Ell-i/RIOT,ant9000/RIOT,OTAkeys/RIOT,kerneltask/RIOT,plushvoxel/RIOT,kaspar030/RIOT,mtausig/RIOT,gebart/RIOT,gebart/RIOT,LudwigKnuepfer/RIOT,biboc/RIOT,authmillenon/RIOT,mtausig/RIOT,jbeyerstedt/RIOT-OTA-update,syin2/RIOT,smlng/RIOT,x3ro/RIOT,neiljay/RIOT,mfrey/RIOT,thomaseichinger/RIOT,toonst/RIOT,ant9000/RIOT,LudwigOrtmann/RIOT