Minor optimization to DefaultRoleService bootstrapAdminUser

[amcclain]

• Resolve possible bootstrapAdminUser setting once, on init, and log if active.
• Simplify getRolesForUser accordingly - this can get called in hot loops with permission checks, want to do anything we can to keep it lean and mean.

[amcclain]

Apologies for the whitespace changes - that's my IDE, promise I am not spending (that much) time fiddling with spacing braces...

[lbwexler]

@amcclain -- love this clarity