add getenv

[ckeyer]

add template function getenv

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[k8s-reviewable]

This change is 

[coveralls]

Coverage remained the same at 47.073% when pulling 52975eb73539729428105fe0b04124f6c4d84cec on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[coveralls]

Coverage remained the same at 47.073% when pulling b8c83f12d028721b24370cad6b5b35669c69ece2 on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[coveralls]

Coverage increased (+0.02%) to 47.088% when pulling b8c83f12d028721b24370cad6b5b35669c69ece2 on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[coveralls]

Coverage remained the same at 47.073% when pulling b8c83f12d028721b24370cad6b5b35669c69ece2 on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[coveralls]

Coverage remained the same at 47.073% when pulling b8c83f12d028721b24370cad6b5b35669c69ece2 on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[aledbf]

@ckeyer please sign the CLA

[coveralls]

Coverage decreased (-0.03%) to 47.043% when pulling e9e8e7264a148ee2d804d291255ac5cb05daafb1 on ckeyer:template_getenv into f9663a8 on kubernetes:master.

[aledbf]

@ckeyer please sign the CLA

[coveralls]

Coverage decreased (-0.02%) to 47.139% when pulling 125b526d760a8fa8ce63c6cbeb2cf2dfc6b52073 on ckeyer:template_getenv into 4601775 on kubernetes:master.

[coveralls]

Coverage remained the same at 47.154% when pulling 7563bf1745a16d338be4fff663744995f1eee317 on ckeyer:template_getenv into 4601775 on kubernetes:master.

[coveralls]

Coverage decreased (-0.02%) to 47.139% when pulling 7563bf1745a16d338be4fff663744995f1eee317 on ckeyer:template_getenv into 4601775 on kubernetes:master.

[ckeyer]

@aledbf PTAL

[coveralls]

Coverage increased (+0.02%) to 47.124% when pulling 87b0584 on ckeyer:template_getenv into 433220d on kubernetes:master.

[aledbf]

/lgtm

[aledbf]

@ckeyer thanks!