llvmpipe: create cs tpool threads in first context creation

stop spawning these from lavapipe enumeration
57 jobs for !10178 with lp_threads in 12 seconds (queued for 20 seconds)
latest detached
Status Job ID Name Coverage
  Sanity
passed #9018666
sanity

00:00:12

 
  Container
manual #9018678
aarch64 manual
arm_build
manual #9018682
windows shell 1809 mesa manual
windows_build_vs2019
manual #9018670
manual
x86_build-base
manual #9018674
manual
x86_test-base
 
  Container 2
created #9018729
android_build
created #9018711
i386_build
created #9018692
kernel+rootfs_amd64
created #9018695
aarch64
kernel+rootfs_arm64
created #9018744
aarch64
kernel+rootfs_arm64-baremetal
created #9018701
aarch64
kernel+rootfs_armhf
created #9018751
aarch64
kernel+rootfs_armhf-baremetal
created #9018715
ppc64el_build
created #9018720
s390x_build
created #9018706
x86_build
created #9018734
x86_test-gl
created #9018739
x86_test-vk
 
  Meson X86 64
created #9018775
meson-clang
created #9018779
meson-clover
created #9018763
meson-clover-testing
created #9018768
meson-gallium
created #9018773
meson-release
created #9018756
meson-testing
created #9018760
meson-testing-asan
created #9018785
meson-vulkan
 
  Build Misc
created #9018789
arm_test
created #9018793
meson-android
created #9018802
aarch64
meson-arm64
created #9018807
aarch64
meson-arm64-asan
created #9018813
aarch64
meson-arm64-build-test
created #9018797
aarch64
meson-armhf
created #9018827
meson-i386
created #9018839
meson-mingw32-x86_64
created #9018834
meson-ppc64el
created #9018830
kvm
meson-s390x
created #9018818
docker windows 1809 mesa
meson-windows-vs2019
 
  Software Renderer
created #9018873
lavapipe-vk
created #9018869
llvmpipe-egl
created #9018865
llvmpipe-gles2
created #9018843
llvmpipe-piglit-cl
created #9018852
llvmpipe-piglit-glslparser
created #9018848
llvmpipe-piglit-quick_gl
created #9018857
llvmpipe-piglit-quick_shader
created #9018861
llvmpipe-traces
 
  Layered Backends
created #9018926
docker windows 1809 mesa
test-d3d12-windows
created #9018893
virgl-gl30-on-gl
created #9018898
virgl-gl31-on-gl
created #9018903
virgl-gl32-on-gl
created #9018877
virgl-gles2-on-gl
created #9018885
virgl-gles31-on-gl 1/2
created #9018890
virgl-gles31-on-gl 2/2
created #9018879
virgl-gles3-on-gl
created #9018907
virgl-traces
created #9018922
zink-lvp-gl
created #9018914
zink-lvp-gles2
created #9018918
zink-lvp-gles3
created #9018911
zink-piglit-quick_gl