Flatten out the structure of Diego staging messages.
Add an error to job presenter if job failed

[#62361748]

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>
Bump vcap-common

Maria Shaldibina (2):
      Use sysctl to determine the number of cpu cores on darwin
      Test general case for num_cores command failing

Signed-off-by: Maria Shaldibina <mariash@pivotallabs.com>