Do nothing when common.bash is sourced multiple times.
Do nothing when common.bash is sourced multiple times.

common.bash may be source 2, 3, or ... times through various nightly.* script calls that source other common-*.bash scripts. This optimization ensures the first one only does work.

r: bradcray

git-svn-id: 88467cb1fb04b8a755be7e1ee1026be4190196ef@22803 3a8e244f-b0f2-452b-bcba-4c88e055c3ca

hildeth/chapel,chizarlicious/chapel,chizarlicious/chapel,chizarlicious/chapel,hildeth/chapel,sungeunchoi/chapel,hildeth/chapel,hildeth/chapel,chizarlicious/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,chizarlicious/chapel,sungeunchoi/chapel,sungeunchoi/chapel,sungeunchoi/chapel,sungeunchoi/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,CoryMcCartan/chapel,hildeth/chapel,hildeth/chapel,chizarlicious/chapel,hildeth/chapel,chizarlicious/chapel