Allow use of "-" symbol in phase names

When using "-P foobar-dev,foobar-test,foobar-prod" as phases, the prefix of channel labels are note handled correctly. You would expect the following structure:

foobar-dev-blablabla
foobar-test-blablabla
foobar-prod-blablabla

But instead you get something like

foobar-dev-blablabla
foobar-dev-foobar-dev-blablabla
...

This patch fixes this.