srctree.bbclass: Don't automatically use git clean.
srctree.bbclass: Don't automatically use git clean.

This should be an opt-in feature.

Signed-off-by: Chris Larson <8cf06b7089d5169434d5def8b2d1c9c9c95f6e71@mvista.com>

sledz/oe,philb/pbcl-oe-2010,sledz/oe,hulifox008/openembedded,rascalmicro/openembedded-rascal,crystalfontz/openembedded,dellysunnymtech/sakoman-oe,JamesAng/goe,openpli-arm/openembedded,mrchapp/arago-oe-dev,xifengchuo/openembedded,crystalfontz/openembedded,anguslees/openembedded-android,rascalmicro/openembedded-rascal,sampov2/audio-openembedded,sampov2/audio-openembedded,philb/pbcl-oe-2010,John-NY/overo-oe,thebohemian/openembedded,xifengchuo/openembedded,buglabs/oe-buglabs,JamesAng/goe,yyli/overo-oe,buglabs/oe-buglabs,buglabs/oe-buglabs,sutajiokousagi/openembedded,SIFTeam/openembedded,dellysunnymtech/sakoman-oe,JamesAng/goe,sutajiokousagi/openembedded,sampov2/audio-openembedded,nx111/openembeded_openpli2.1_nx111,dellysunnymtech/sakoman-oe,John-NY/overo-oe,giobauermeister/openembedded,Martix/Eonos,openpli-arm/openembedded,buglabs/oe-buglabs,nzjrs/overo-openembedded,anguslees/openembedded-android,nx111/openembeded_openpli2.1_nx111,dave-billin/overo-ui-moos-auv,rascalmicro/openembedded-rascal,libo/openembedded,trini/openembedded,SIFTeam/openembedded,openembedded/openembedded,sentient-energy/emsw-oe-mirror,xifengchuo/openembedded,yyli/overo-oe,openembedded/openembedded,sentient-energy/emsw-oe-mirror,trini/openembedded,anguslees/openembedded-android,John-NY/overo-oe,SIFTeam/openembedded,libo/openembedded,mrchapp/arago-oe-dev,nzjrs/overo-openembedded,sentient-energy/emsw-oe-mirror,bticino/openembedded,openpli-arm/openembedded,nzjrs/overo-openembedded,dave-billin/overo-ui-moos-auv,trini/openembedded,JamesAng/goe,sledz/oe,BlackPole/bp-openembedded,Martix/Eonos,crystalfontz/openembedded,xifengchuo/openembedded,openpli-arm/openembedded,scottellis/overo-oe,SIFTeam/openembedded,buglabs/oe-buglabs,JamesAng/oe,BlackPole/bp-openembedded,bticino/openembedded,SIFTeam/openembedded,xifengchuo/openembedded,sentient-energy/emsw-oe-mirror,openembedded/openembedded,nx111/openembeded_openpli2.1_nx111,thebohemian/openembedded,hulifox008/openembedded,hulifox008/openembedded,nzjrs/overo-openembedded,dave-billin/overo-ui-moos-auv,bticino/openembedded,scottellis/overo-oe,philb/pbcl-oe-2010,Martix/Eonos,rascalmicro/openembedded-rascal,trini/openembedded,mrchapp/arago-oe-dev,nzjrs/overo-openembedded,hulifox008/openembedded,BlackPole/bp-openembedded,sledz/oe,openembedded/openembedded,Martix/Eonos,yyli/overo-oe,nx111/openembeded_openpli2.1_nx111,giobauermeister/openembedded,John-NY/overo-oe,bticino/openembedded,openembedded/openembedded,trini/openembedded,xifengchuo/openembedded,rascalmicro/openembedded-rascal,openembedded/openembedded,openpli-arm/openembedded,BlackPole/bp-openembedded,thebohemian/openembedded,sentient-energy/emsw-oe-mirror,openembedded/openembedded,rascalmicro/openembedded-rascal,JamesAng/oe,JamesAng/oe,libo/openembedded,sampov2/audio-openembedded,philb/pbcl-oe-2010,Martix/Eonos,openembedded/openembedded,openembedded/openembedded,yyli/overo-oe,sutajiokousagi/openembedded,dave-billin/overo-ui-moos-auv,sampov2/audio-openembedded,giobauermeister/openembedded,crystalfontz/openembedded,sutajiokousagi/openembedded,dave-billin/overo-ui-moos-auv,thebohemian/openembedded,scottellis/overo-oe,philb/pbcl-oe-2010,scottellis/overo-oe,hulifox008/openembedded,JamesAng/oe,sentient-energy/emsw-oe-mirror,sledz/oe,thebohemian/openembedded,bticino/openembedded,rascalmicro/openembedded-rascal,libo/openembedded,nx111/openembeded_openpli2.1_nx111,hulifox008/openembedded,John-NY/overo-oe,mrchapp/arago-oe-dev,libo/openembedded,dellysunnymtech/sakoman-oe,openembedded/openembedded,giobauermeister/openembedded,sutajiokousagi/openembedded,BlackPole/bp-openembedded,JamesAng/oe,anguslees/openembedded-android,crystalfontz/openembedded,anguslees/openembedded-android,giobauermeister/openembedded,sutajiokousagi/openembedded,John-NY/overo-oe,giobauermeister/openembedded,philb/pbcl-oe-2010,dellysunnymtech/sakoman-oe,nx111/openembeded_openpli2.1_nx111,giobauermeister/openembedded,SIFTeam/openembedded,libo/openembedded,dellysunnymtech/sakoman-oe,openembedded/openembedded,BlackPole/bp-openembedded,JamesAng/goe,yyli/overo-oe,buglabs/oe-buglabs,BlackPole/bp-openembedded,philb/pbcl-oe-2010,thebohemian/openembedded,JamesAng/goe,buglabs/oe-buglabs,openpli-arm/openembedded,Martix/Eonos,thebohemian/openembedded,dave-billin/overo-ui-moos-auv,dave-billin/overo-ui-moos-auv,nzjrs/overo-openembedded,sledz/oe,dellysunnymtech/sakoman-oe,dellysunnymtech/sakoman-oe,rascalmicro/openembedded-rascal,nx111/openembeded_openpli2.1_nx111,nx111/openembeded_openpli2.1_nx111,xifengchuo/openembedded,xifengchuo/openembedded,sledz/oe,trini/openembedded,buglabs/oe-buglabs,yyli/overo-oe,bticino/openembedded,xifengchuo/openembedded,scottellis/overo-oe,mrchapp/arago-oe-dev,yyli/overo-oe,mrchapp/arago-oe-dev,scottellis/overo-oe,sampov2/audio-openembedded,sutajiokousagi/openembedded,giobauermeister/openembedded,openpli-arm/openembedded,hulifox008/openembedded,sentient-energy/emsw-oe-mirror,dellysunnymtech/sakoman-oe,mrchapp/arago-oe-dev,scottellis/overo-oe,anguslees/openembedded-android,nzjrs/overo-openembedded,giobauermeister/openembedded,crystalfontz/openembedded,JamesAng/oe,sampov2/audio-openembedded,Martix/Eonos,anguslees/openembedded-android,crystalfontz/openembedded,John-NY/overo-oe,trini/openembedded,SIFTeam/openembedded,JamesAng/oe,yyli/overo-oe,bticino/openembedded,libo/openembedded,JamesAng/goe