fn CLI update doesn't support annotation values that aren't JSON blobs

[gviedma-zz]

According to https://github.com/fnproject/docs/blob/master/fn/develop/annotations.md it should be possible to specify an annotation value which is just a plain string. Currently, the CLI does not allow this, instead requiring that the value must be a parseable JSON string.

For example:

fn update function myapp myfn --annotation someannotation="foo" 

fails with Unable to parse annotation value 'foo'. Annotations values must be valid JSON strings.

Performing the same operation using curl against the fn REST API succeeds however.

[gviedma-zz]

Turns out this is not an issue with the CLI but rather with the shell stripping out the quotes. Adapting the above example to:

fn update function myapp myfn --annotation someannotation='"foo"'

provides the right behavior.