We allow characters in the ID of an ILM policy that will result in an invalid snapshot name.

For example, an ILM policy with the name `mypolicy-*` can be created, however, the generation of the snapshot name in this line:

https://github.com/elastic/elasticsearch/blob/befb6faafc9fca327fd3cea2d0ab328a521c4e65/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/GenerateSnapshotNameStep.java#L81

Results in the `mypolicy-*` being part of the snapshot name, which the snapshot service then disallows. We should strip these invalid characters from the snapshot name.
server/src/main/java/org/elasticsearch/common/Strings.java
* Check whether the given CharSequence has actual text.
     * More specifically, returns <code>true</code> if the string not <code>null</code>,
     * its length is greater than 0, and it contains at least one non-whitespace character.
     * <pre>
     * StringUtils.hasText(null) = false
     * StringUtils.hasText("") = false
     * StringUtils.hasText(" ") = false
     * StringUtils.hasText("12345") = true
     * StringUtils.hasText(" 12345 ") = true
     * </pre>
     *
     * @param str the CharSequence to check (may be <code>null</code>)
     * @return <code>true</code> if the CharSequence is not <code>null</code>,
     *         its length is greater than 0, and it does not contain whitespace only
     * @see java.lang.Character#isWhitespace
     */
    public static boolean hasText(CharSequence str) {
        if (hasLength(str) == false) {
            return false;
        }
        int strLen = str.length();
        for (int i = 0; i < strLen; i++) {
            if (Character.isWhitespace(str.charAt(i)) == false) {
                return true;
            }
        }
        return false;
    }
    /**
     * Check whether the given String has actual text.