misc/backup-mongodb: improve usage instructions
misc/backup-mongodb: improve usage instructions

RichardKnop/tsuru,ArxdSilva/tsuru,hcxiong/tsuru,guilhermebr/tsuru,cgvarela/tsuru,gciotta/tsuru,tsuru/tsuru,hcxiong/tsuru,hugoantunes/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,ggarnier/tsuru,jblancett/tsuru,ggarnier/tsuru,jblancett/tsuru,gciotta/tsuru,firebitsbr/tsuru,tuxmonteiro/tsuru,tsuru/tsuru,4eek/tsuru,kgrvamsi/tsuru,RichardKnop/tsuru,ArxdSilva/tsuru,tsuru/tsuru,firebitsbr/tsuru,ArxdSilva/tsuru,tuxmonteiro/tsuru,cezarsa/tsuru,gwmoura/tsuru,gwmoura/tsuru,gwmoura/tsuru,ggarnier/tsuru,Endika/tsuru,4eek/tsuru,kgrvamsi/tsuru,guilhermebr/tsuru,gciotta/tsuru,cezarsa/tsuru,Endika/tsuru,RichardKnop/tsuru,cezarsa/tsuru,4eek/tsuru,cgvarela/tsuru,mderaldo/tsuru,ggarnier/tsuru,cgvarela/tsuru,jblancett/tsuru,tuxmonteiro/tsuru,guilhermebr/tsuru,kgrvamsi/tsuru,hugoantunes/tsuru,mderaldo/tsuru,mderaldo/tsuru,hcxiong/tsuru,firebitsbr/tsuru,tsuru/tsuru,guilhermebr/tsuru,Endika/tsuru