fix regression whereby main thread didn't get TLS relocations

fix regression whereby main thread didn't get TLS relocations

commit ffab43602b5900c86b7040abdda8ccf6cdec95f5 broke this by moving
relocations after not only the allocation of storage for the main
thread's static TLS, but after the copying of the TLS image. thus,
relocation results were not reflected in the main thread's copy. this
could be fixed by calling __reset_tls after relocations, but instead
split the allocation and installation before/after relocations so that
there's not a redundant copy.

due to commit 71af5309874269bcc9e4b84ea716fab33d888c1d, updating of
static_tls_cnt needs to be kept with allocation of static TLS, before
relocations, rather than after installation.