Description of problem: miq_custom_set allows you to name a custom attribute with a space, colon, etc.

It should have a validation that fails.
Found in:  https://bugzilla.redhat.com/show_bug.cgi?id=1553750#c15

Note, this change needs to allow our existing provider/ems refreshes/scans to properly set the custom attribute as they currently already do.  We cannot break existing code for refreshes and vm scans in order to fix this bug.



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from: https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS

SQL identifiers and key words must begin with a letter (a-z, but also letters with diacritical marks and non-Latin letters) or an underscore (_). Subsequent characters in an identifier or key word can be letters, underscores, digits (0-9), or dollar signs ($). Note that dollar signs are not allowed in identifiers according to the letter of the SQL standard, so their use might render applications less portable. The SQL standard will not define a key word that contains digits or starts or ends with an underscore, so identifiers of this form are safe against possible conflict with future extensions of the standard.