haproxy: Update HAProxy to v2.1.5

haproxy: Update HAProxy to v2.1.5

- Update haproxy download URL and hash
- This version introduces backtrace-support via backtrace(), however, it must be disabled because neither MUSL nor UCLIBC support it (build fails because of missing execinfo.h)
- Our previous UCLIBC patch is now obsolete and has been removed. We now only disable libcrypt support.
- A new patch was backported from the haproxy dev-branch which fixes an IFDEF which should only allow GLIBC to use dladdr1 and make builds fall back to dladdr when using other c-libs. The previous logic was bogus and broke the build on UCLIBC.

Signed-off-by: Christian Lachner <redacted>