fetch-configlet: make some variables local

[ee7]

Reduce the number of globals.

From e.g. the Google Shell Style Guide:

Ensure that local variables are only seen inside a function and its children by using local when declaring them. This avoids polluting the global name space and inadvertently setting variables that may have significance outside the function.

Declaration and assignment must be separate statements when the assignment value is provided by a command substitution; as the local builtin does not propagate the exit code from the command substitution.

my_func2() {
 local name="$1"

 # Separate lines for declaration and assignment:
 local my_var
 my_var="$(my_func)"
 (( $? == 0 )) || return

 …
}

my_func2() {
 # DO NOT do this:
 # $? will always be zero, as it contains the exit code of 'local', not my_func
 local my_var="$(my_func)"
 (( $? == 0 )) || return

 …
}