Description of problem:
Build can't get the correct password from secret if username in secret is different with username in source repo.
When create secret with username and password,the secret will generate two separated data 'username' and password.So if username in secret is different with username in source repo, shouldn't influence the password validation.

Version-Release number of selected component (if applicable):
devenv-fedora_2459

How reproducible:
always

Steps to Reproduce:
1.Generate a secret with a no-existing username and correct password for correct username xiuwang
oc secrets new-basicauth mysecret --username=xiuwangnoexisting --password=redhat123
2.Edit buildconfig to include mysecret secret and add username into source repo
  source:
    git:
      uri: https://xiuwang@bitbucket.org/xiuwang/ruby-hello-world.git
    sourceSecret:
      name: mysecret
3.Create app and check new build

Actual results:
step 3:
oc start-build ruby-sample-build --follow 
E1012 08:30:22.744819       1 git.go:102] Clone failed: fatal: could not read Password for 'https://xiuwang@bitbucket.org': No such device or address
F1012 08:30:22.745804       1 builder.go:54] Build error: exit status 128


Expected results:
Should build successfully or tip more friendly.

Additional info:
Build will succeed with secret only with password, and username in source repo.

1.Create secret only with password
oc secrets new-basicauth mysecret1 --password=redhat123
2.Use new mysecret1 in buildconfig
  source:
    git:
      uri: https://xiuwang@bitbucket.org/xiuwang/ruby-hello-world.git
    sourceSecret:
      name: mysecret1
3.Trigger build
Build will succeed.